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The definitive motor oil bible.

AE Hass said:
Chapter One - Motor Oil 101

I think it is time to go over passenger car automotive engine oils in detail. I will be writing several articles to be published soon so I will try to get some of it out here. I feel this is a very general topic for all car owners on this board.

This is a very difficult topic to comprehend. Everybody including good mechanics think they are experts in this field but few understand engine oils. Most of what I hear is the opposite of the truth. It is however easy to see how people get mixed up as there is always some truth to the misconception.

Please forgive me if I am too wordy or even verbose at times. I will be redundant for certain. This will be in areas that people have to hear things over and over again to get it right. Some will never be able to understand these concepts unfortunately. I base my thoughts on those whom I have been listening to in various automotive chat rooms and discussion with mechanics. I will try to minimize technical terms and be somewhat vague rather than exact. I will round and average numbers to make the point simple rather than mathematically exact. Thickness has the same meaning as viscosity. Viscosity is a measure of the resistance of a fluid (liquid or gas) to flow. Fluids with high viscosity, such as molasses, flow more slowly than those with low viscosity, such as water. Again, I am trying to explain general principals as I know them.

The greatest confusion is because of the way motor oils are labeled. It is an old system and is confusing to many people. I know the person is confused when they say that a 0W-30 oil is too thin for their engine because the old manual says to use 10W-30. This is wrong.

More confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. In fact this is the problem. It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup.

Oils are chosen by the manufacturer to give the right thickness at the normal operating temperature of the engine. I will say this average oil temperature is 212 F, the boiling point of water. On the track that temperature is up to 302F. It is important to realize that these are two different operating environments and require different oils.

I will discuss driving around town first. Everything I say will be based on these conditions. At a later time I will discuss track conditions. Everything I say will be as accurate as possible without looking everything up and footnoting. I am trying to be general not ultra specific.

One thing that is no longer important is the ambient temperature. Older automotive owner manuals often recommended one oil for the summer and another for the winter. This is still necessary for air cooled engines but is no longer a consideration in pressurized water cooled engines. These engine blocks are kept at around 212 F all year round. The oil is around the same temperature as well. This allows for a single weight oil all year round. Again, this is not the same as on the track where the coolant temperature is slightly higher and the oil temperature is much higher.

Please forget those numbers on the oil can. They really should be letters as AW-M, BW-N or CW-P. The fact that we are dealing with a system of numbers on the can makes people think that they represent the viscosity of the oil inside the can. The problem is that the viscosity of oil varies with its temperature. A “30” weight oil has a viscosity of 3 at 302 F ( 150 C ) and thickens to 10 at 212 F ( 100 C ). It further thickens to a viscosity of 100 at 104 F ( 40 C ) and is too thick to measure at the freezing point of 32 F ( 0 C ).

30 weight oil:

Temperature ( F )....Thickness

32..........................250 (rough estimate)

The automotive designers usually call for their engines to run at 212 F oil and water temperature with an oil thickness of 10. This is the viscosity of the oil, not the weight as labeled on the oil can. I want to stay away from those numbers as they are confusing. We are talking about oil thickness, not oil can labeling. This will be discussed later. Forget the numbers on that oil can for now. We are only discussing the thickness of the oil that the engine requires during normal operating conditions.

The engine is designed to run at 212 F at all external temperatures from Alaska to Florida. You can get in your car in Florida in September and drive zig-zag to Alaska arriving in November. The best thing for your engine would be that it was never turned off, you simply kept driving day and night. The oil thickness would be uniform, it would always be 10. In a perfect world the oil thickness would be 10 at all times and all temperatures.

If the thickness of oil was 10 when you got in your car in the morning and 10 while driving it would be perfect. You would not have to warm up your engine. You could just get in the car and step on the gas. There would be little wear and tear on you engine, almost none. Unfortunately the world is not perfect.

The night before when you drove home from work the car was up the the correct operating temperature and the oil was the correct thickness, 10. Over night the engine cooled to room temperature and the oil thickened. It is 75 F in the morning now (I do live in Florida). The oil thickness is now around 150. It is too thick to lubricate an engine designed to run with an oil having a thickness of 10.

It is time to introduce the concept of lubrication. Most believe that pressure = lubrication. This is false. Flow = lubrication. If pressure was the thing that somehow lubricated your engine then we would all be using 90 weight oil. Lubrication is used to separate moving parts, to keep them from touching. There is a one to one relationship between flow and separation. If you double the flow you will double the separation pressure in a bearing. The pressure at the bearing entrance is irrelevant.

In fact the relationship between pressure and flow is in opposition. If you change your oil to a thicker formula the pressure will go up. It goes up because the resistance to flow is greater and in fact the flow must go down in order for the pressure to go up. They are inversely related. Conversely if you choose a thinner oil then the pressure will go down. This can only occur if the flow has increased.

It seems then that we should all be using the thinnest oil money can buy. This is partly true. Let me use my 575 Ferrari Maranello as an example. I drive this car around town. The manual of this car states the target pressure is 75 PSI at 6,000 RPM. The gold standard is that all engines should have a pressure of 10 PSI for every 1,000 RPM of operation, not more, not less. After all, you do need some pressure to move that oil along, but only enough pressure, not more. More pressure is not better, it can only result from the impedance of oil flow. Remember that oil flow is the only thing that does the lubricating.

Note that Ferrari is not saying what thickness of oil to use. That can only be determined by experimentation. My engine oil temperature is running around 185 F as I drive around town on a hot Florida summer day. I have found that the thinnest oil I can buy that is API / SAE certified is Mobil 1’s thinnest oil. Even with this oil I get 80 PSI at 2,000 RPM. It is too thick for my application yet it is the thinnest oil money can buy. If I was on a hot Florida track in mid-summer the oil temperature would probably get up to 302 F. I will guess that the pressure would only be 40 PSI at 6,000 RPM. The oil I am using would not meet the requirement of 75 PSI at 6,000 RPM from Ferrari. I would have to choose a thicker oil for this racing situation. The oil I use now would be too thin at that very high temperature. (This is only partly true. Higher RPM running engines use thinner and thinner oils to get more and more flow. I will discuss this later).

High flow does more than lubricate. It is one of the things used to cool the hottest parts of your engine, the pistons, valve areas and bearings. This cooling effect is as important as lubrication in your engine. If your engine is running hot use a thinner oil. The flow will increase and so will the cooling. This is even more important in the racing condition.

Let us go back to the Ferrari manual. My older 550 Maranello only specified 5W-40 Shell Helix Ultra as the oil to use in all conditions. This car was designed for racing. As it turns out Ferrari now recognizes that not every owner races their cars. The newer 575 manual now states to use 0W-40 for around town situations even though Shell does not make this oil in the Helix Ultra formulation at this writing. They also recommend the 5W-40 by Shell if you insist on the Shell product. It is also the recommended oil for most racing conditions.

Ferrari recommends Helix Ultra Racing 10W-60 “for hot climate conditions racing type driving on tracks”. Note that they now realize the difference between the daily urban driver like me and the very different racing situation. These are widely different circumstances. I want to emphasize that they only want you to use this oil while racing in “hot climate conditions”. If you are racing in Watkins Glen up north use the 5W-40. If you are racing in Sebring in the middle of the Florida summer use the 10W-60. Around town in any climate, use the 0W-40.

It is time to dispel the notion that 0W-30 oil is too thin when our manual calls for 10W-30. A 0W-30 is always the better choice, always. The 0W-30 is not thinner. It is the same thickness as the 10W-30 at operating temperatures. The difference is when you turn your engine off for the night. Both oils thicken over the evening and night. They both had a thickness, a viscosity of 10 when you got home and turned your engine off. That was the perfect thickness for engine operation.

As cooling occurs and you wake up ready to go back to work the next day the oils have gotten too thick for your engine to lubricate properly. It is 75 F outside this morning. One oil thickened to a viscosity of say 90. The other thickened to a viscosity of 40. Both are too thick in the morning at startup. But 40 is better than 90. Your engine wants the oil to have a thickness of 10 to work properly. You are better off starting with the viscosity of 40 than the honey - like oil with a viscosity of 90.

I repeat: More confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. In fact this is the problem.

This is the end of lesson number one.


About the author:
Dr. Haas is a physician and surgeon. He graduated from the University of Florida with a degree in biochemistry with honors. He studied motor oils since high school where he did independent studies on this topic. He studied the properties of viscosity.

When he was a general surgery resident in Chapel Hill he studied the flow mechanics of human blood. Today he continues his research by discussion of oil products with chemists in the field and chemists from the oil manufacturers.

He has personal racing experience in Formula Super Vee. He is his own Lamborghini and Ferrari as well as Mercedes mechanic.

Motor Oil 102

Chapter two. It gets more difficult.

We left off discussing that a 0W-30 weight oil is not thinner than a 10W-30 oil. They both have the same thickness at operating temperature. The 0W-30 simply does not get as thick on cooling as the 10W-30. Both are still way to thick to lubricate an engine at startup.

I have heard several people say that Porsche specifically prohibits a 0W-XX engine oil, that it is too thin. Now here is the partial truth I spoke of earlier. We will discuss multigrade oils. Earlier we said that a straight 30 weight oil has a thickness of 10 at the normal operating temperature of your engine. The multigrade oils 0W-30 and 10W-30 also have a thickness of 10 at 212 F.

The difference is at 75 F, your startup temperature in the morning.

Oil type... Thickness at 75 F...Thickness at 212 F

Straight 30...... 250......................10
0W-30..............40 ......................10

Straight 10........30....................... 6

Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. But it does not have far to go before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. It cannot flow and therefore cannot lubricate. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil ways. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less.

Note that a straight 10 weight oil is also too thick for your engine at startup. It has a thickness of 30. Yet at operating temperatures it is too thin having a thickness of 6. It needs to be around 10. The oil companies have added viscosity index improvers or VI to oils to solve this dilemma. They take a mineral based oil and add VI improvers so that it does not thin as as much when it gets hotter. Now instead of only having a thickness of 6 when hot it has a thickness of 10, just as we need.

The penalty is the startup thickness also goes up to 100. This is better than being up at 250 as a straight 30 weight oil though. Oil with a startup thickness of 100 that becomes the appropriate thickness of 10 when fully warmed up is called a 10W-30 weight motor oil. This is NOT as thick as a straight 30 weight oil at startup and it is NOT as thin as a straight 10 weight oil at full operating temperature.

The downside of a mineral based multigrade oil is that this VI additive wears out over time and you end up with the original straight 10 weight oil. It will go back to being too thin when hot. It will have a thickness of 6 instead of 10. This may be why Porsche (according to some people) does not want a 0W-30 but rather a 10W-30. If the VI wears out the 0W-30 will ultimately be thinner, a straight 0 weight oil. When the VI is used up in the 10W-30 oil it too is thinner. It goes back to a straight 10 weight oil. They are both still too thick at startup, both of them. The straight 0 weight oil, a 5 weight oil and a 10 weight oil are all too thick at startup.

This is just theory however. With normal oil change intervals the VI improver will not wear out and so the problem does not really exist. In fact, oils do thin a little with use. This is partly from dilution with blow by gasoline and partly from VI improvers being used up. What is more interesting is that with further use motor oils actually thicken and this is much worse than the minimal thinning that may have occurred earlier.

Synthetic oils are a whole different story. There is no VI improver added so there is nothing to wear out. The actual oil molecules never wear out. You could almost use the same oil forever. The problem is that there are other additives and they do get used up. I suppose if there was a good way to keep oil clean you could just add a can of additives every 6 months and just change the filter, never changing the oil.

When the additives wear out in a synthetic oil it still has the same viscosity. It will not thin as a mineral oil. The fear that some say Porsche has that oils thin when the VI runs out is not applicable to these synthetic oils. These oils will always have the correct thickness when hot and will still be too thick at startup as with all oils of all types, regardless of the API / SAE viscosity rating.

Automotive engine manufacturers know these principals of motor oils. They know there is thinning or thickening that will occur. They take these things into account when they write that owners manual. Mineral oil change recommendations will generally include shorter time intervals than those of synthetic oils.

The reality is that motor oils do not need to be changed because they thin with use. It is the eventual thickening that limits the time you may keep oil in your engine. The limit is both time itself (with no motor use) and/or mileage use.

End of part two.

Motor Oil 103

Chapter Three.

You have a synthetic mind.

Let us compare mineral and synthetic oils. I will not talk about chemical but rather functional differences. We discussed before how mineral oils are too thick at startup yet too thin when hot. The viscosity was corrected with the hot engine by adding VI improvers.

A 10W-30 multigrade mineral based oil is made from a 10 weight oil and has VI improvers added to thicken the product in a 212 F engine. It acts as a 30 weight oil when hot. It acts more as a 10 weight oil at startup. I remind you that a 10 or 5 or 2 weight oil is still too thick to provide lubrication at startup. They are all too thick at startup. There is currently no engine oil thin enough to operate correctly at startup. They all cause excessive wear at startup. Again, we are discussing the needs of my single hypothetical engine for around town driving.

Oil type.. Thickness at 75 F ..Thickness at 212 F

Straight 30..........250....................10

Straight 10..........30.....................6
Straight 5...........20.....................4
Straight 2...........15.....................3
Straight 0...........12.....................3 est.

A 10W-30 synthetic oil is based on a 30 weight oil. This is unlike the counterpart mineral oil based on a 10 weight oil. There is no VI improver needed. The oil is already correct for the normal operating temperature of 212 F. It has a thickness of 10 while you drive to work. It will never thin yet has the same long term problem as the mineral based oil. They both thicken with extended age.

Synthetic oils are derived in the laboratory. They are pure, usually nearly clear. I describe mineral based motor oils as a distilled, concentrated product. The impurities need to be removed from the raw petroleum. These oils are therefore less clean and contain many impurities. Again, the problem is really more of theory than practice but the difference does exist.

People repeatedly say that synthetic oils are more stable in a hot engine. I hear that they lubricate better. The answer is yes and no. Oil molecules do not break down, just the additives. Generally, the synthetic oils do not have VI improvers so have less to lose.

There are some properties of synthetic oils that actually result is less wear than with mineral oils. These help increase your gas mileage as well. Due to a reduction of internal friction of the synthetic oil your engine will run a bit cooler. Wear increases as temperature increases, all other things being constant.

A main advantage that the synthetic has over the mineral based oil is the ability to lubricate at startup. Both types of oil have the same specifications at 104 F, 212 F and 302 F. It is the startup viscosity characteristics that separate these oils. Synthetic oils do not thicken as much on cooling. They have better fluidity as the temperature drops.

A synthetic oil that is labeled as 10W-30 is less honey like as a mineral based 10W-30 motor oil at startup. They both have a thickness of 10 at normal operating temperatures. At 75 F the synthetic is not as thick. At 32 F the difference between the two is even greater. At 0 F the mineral oil is useless yet the synthetic works fairly well. Just keep the RPM to a minimum.

At temperatures below zero you will not be able to start your car with mineral oils while the synthetic oils may be used to -40 or - 50 F. Oils are so thick that the normal method of viscosity measurement is not possible. Instead we measure if the oil can even be pumped or poured. Again, we are only discussing a single category of oil, the multigrade 10W-30 API / SAE grade.

I took an except from the web about Mobil 1 oils. They compared a 5W-30 synthetic Mobil 1 oil to a mineral based 10W-30 and a 10W-40 in ice cold conditions. The engine turned over at 152 RPM with the synthetic 5W-30 Mobil 1. The 10W-30 and 10W-40 mineral oils turned over at 45 and 32 RPM respectively. Neither of those engines started.

Motor oil becomes permanently thicker with exposure to northerly winter type weather. This is more of a problem to mineral based oils. Waxes form. This is why it is a bad idea to even store a bottle of oil in a cold garage. It goes bad on the garage self just because it is exposed to the cold.

To recap, synthetic oils have similar characteristics as mineral oils at operating temperatures. The synthetic oil will however be less honey - like at startup even though it has the same API / SAE rating. Yet the synthetic 10W-30 weight oil is based on a heavier 30 weight oil while the mineral based 10W-30 oil is based on a thinner 10 weight oil. They are both similar at operating temperatures yet the 30 weight based synthetic is actually less thick at startup and much less honey - like at low temperatures. This is the opposite of what common sense dictates.

This is worth repeating: The synthetic 10W-30 weight oil is based on a heavier 30 weight oil while the mineral based 10W-30 oil is based on a thinner 10 weight oil. They are both similar at operating temperatures yet the 30 weight based synthetic is actually less thick at startup and much less honey - like at low temperatures. This is the opposite of what common sense dictates.

As one can see this is no easy topic. Are you with me?

Motor Oil 104


It is not what we thought.

Now let us finish talking about the differences of mineral verses synthetic oils. I will compare the same weigh or grade of oils showing that the operating viscosities are the same whereas the startup viscosities vary:

Mineral oil:

Oil type...Thickness at 75 F... at 212 302 F

Straight 30..........250....................10..........3
0W-30..........There are none in this range......

Synthetic oil:

Oil type...Thickness at 75 F... at 212 302 F

Straight 30...........100...................10...........3

Since the synthetic oil thickens less on shutdown your startup will be easier and so will the stress on your engine. This is perhaps the best thing the synthetic class has over the mineral based oils.

People sometimes use a thicker oil to minimize gasket leaks. This seems obvious to me. Repair the gasket. Do not destroy your engine with an oil that is too thick for proper function.

Some people have said they use thicker oils because they only use their cars every 2, 3 or 4 weeks. They are afraid that thin oils will fall off the engine parts and result in a lack of lubrication at startup. Think about your lawn mower over the winter. I gets gummed up solid. The oil and fuel thicken over time resulting in engine failure. Anyway, oil on the surface of parts does not lubricate. It is the FLOW of oil between parts that lubricates. Thick, old, waxy oil can only be bad.

I have seen several car owner manuals that are now stating that oils do not need to be changed but every 7,500 miles or more. The same manual also states OR every 12 months, whichever occurs first. My feeling is that you can probably go 5,000 miles on the average (in a sports car) but you must change your oil in the spring time at a minimum, particularly up north. Oils form waxes in icy cold weather. There is a permanent thickening of the oil.

Some automotive manufacturers are backing down on oil change intervals to 5,000 miles or less and some advocate changing the oil at least every 6 months as well. I think this is because of the tendency for oils to thicken in very hot engines (not ambient conditions, just hot engines). Also because of thickening from the cold of winter and from sludge build up that cannot be filtered out.

I truly believe that oil is much better being too thin than too thick. Over the years we have been going to thinner and thinner oils despite hotter engines with turbos and the like. The tendency is that people figure they need a 40 weight oils but then use a 50 instead. Better thinking is that if you think you need a 40, use a 30 weight oil instead. I firmly believe this based on all I know about oils.

As it turns out synthetic oils do cling to parts better as they have higher film strength than mineral oils. Synthetics are thinner overall. They have greater slipperiness. Yet they stick better to engine parts. Again, this concept is the opposite of normal thinking.

The thickness of moving oil is measured in centiStokes or cS. Most engines want the oil viscosity to be around 10 cS at normal operating temperature. The really thick multigrade oils have a viscosity of 20 cS at operating temperature. One is not twice as thick as the other, it is only 10 cS thicker.

As we increase the heat from 212 F to 302 F the most commonly recommended oil thins from 10 cS to 3 cS. The thicker oil drops from 20 cS to 4 cS. Note that in a very hot engine the difference between the two oils is now only 1 - 2 cS. In other words they have about the same thickness. There is little advantage to a thicker based oil as a 20W-50 at very high temperatures. No, the 4 cS oil is not twice as thick as the 2 or 3 cS oil. This difference is almost insignificant.

There is a huge advantage of using the thinner, 10W-30 at startup where 90 percent of the engine wear occurs. At 75 F the thicker oil has a viscosity in the range of 250 cS while the thinner oil has a viscosity of 100 cS. The thicker stuff is 150 cS thicker. This is a very big difference. I am using the 20W-50 as my thicker oil example here.

People are always asking about adding things as Slick 50 into the oil tank. Do not do this. The oil companies and engine manufacturers work together very hard to give you the product you need. Engines are running hotter, longer with more BHP from less CID. Smaller, more efficient engines are getting us more MPG and yet better acceleration. These engines last longer and are more reliable.

Part of that reason is the nature of the lubricants. There is a lot of competition to get us the best working motor oil. Independent additives cannot make the oil better and in many cases makes things worse. There have been engine failures as a result of adding some of these aftermarket additives to motor oil.

Motor oil that is labeled for RACING ONLY is not usable for every day driving. Often these have more additives that are toxic to your catalytic converters and the environment. These oils generally do not have detergents. These are very important for your engine unless you plan on taking it apart every few weeks and cleaning every single surface. The oils do not meet the API / SAE requirements for ratings as SJ, SL or now SM.

You do not need to use the exact oil type and brand that your car manual tells you to use. Oils are pretty general. They are not that different. Ferrari is married to Shell. If you call them up and ask to use Valvoline instead they will tell you that they have not tested that brand in their cars. They only tested the engine with Shell oils. They cannot comment on the performance of other oils in their engines. This is a fair statement. The reality is that the Shell and Valvoline oils of the same specification (viscosity, API and SAE ratings, synthetic or not) are very similar. ( I do have my bullet proof vest on ).

People often say that their old 1980 car manual says to use a specific Brand-X motor oil. They keep trying to locate these older oils. First, just about any oil brand that meets the original specifications will do. Second, all oils are much, much better now. They are all much better. One could say that synthetic oils are better than mineral oils but it is hard to say that one brand is that much better than any other. Personally, I do stick to the big names. It does not mean that small motor oil companies are not as good. They could be better for all I know.

Using an oil that is less thick at startup has other benefits. Let us compare a synthetic 10W-30 to a mineral based 10W-30. Both give you a viscosity of 10 cS at normal engine operating temperatures. They both thin to 3 cS at high temperatures. At 75 F tomorrow morning the story will be different. The startup viscosity of the synthetic will be 50 whereas the mineral based 10W-30 will be 75. Again, both are too thick at startup but the synthetic will cause less startup time period wear and tear. You will get a little better gas mileage too.

The synthetic lubricated engine will turn over easier. This has the effect of using less power from your starter motor. It will last longer. Your battery has less of a current draw. This will also last longer. The battery was discharged less during the start so the alternator will rob less power from your engine to recharge. The alternator lasts longer and you get a little better gas economy. The only downside of synthetic lubricants is the cost. They cost 2 or 3 times as much as mineral based oils. Never-the-less I use plain Pennzoil multigrade mineral based 5W-20 in my Ford Expedition. This oil is thin enough at startup to have many of the attributes I just mentioned.

Motor Oil 105

Chapter Five.

Let’s use top gear:

Let’s go racing. I will discuss driving in traffic jams in the Florida summer as well as racing in Sebring though there is no commonality. People lump these two driving situations together but there is no overlap.

On the race track one usually uses all the BHP their engine can give them. You briefly step on the brakes for the corner then put the pedal to the metal the rest of the time. Your oil will get up to 302 F, but your cooling system is around 212 F. The engine produces tremendous heat but can only pass it off so fast to the cooling system. There is a lot of air moving past the cooling radiator so the antifreeze / coolant is able to get rid of the extra heat from this part of the system with relative ease.

The temperature of oil on your gauge is not as hot as it really gets. This temperature is an average with oil from different parts of the motor. Some parts are hotter than others. It is said that some of the oil gets as hot as 400 or 500 F in these racing situations.

In an earlier section I said that thicker oils are usually needed in racing situations but not necessarily. Remember that a major function of oil is to cool the inside of your engine. In ASTM D 4485 3.1.4: “Terminology: Engine oil- a liquid that reduces friction and wear between moving parts within an engine, and also serves as a coolant.” Since the oil with a viscosity of 10 cS at 212 F thins to a viscosity of 3 cS at 302 F we will get more flow. The pressure will go down some as well. This is OK as long as we have a minimum of pressure to move the oil.

This increased flow will result in increased cooling by the oil. This is a good thing. You would probably want more oil flow in these situations and you get it. The hotter oil thins and this increases flow. The higher flow works harder to separate the engine parts that are under very high stress. It all works out for the better. Higher revving engines need thinner oils. You do not necessarily need to go to a thicker oil while racing. Only experimentation will tell.

The best way to figure out what viscosity of oil you need is to drive the car in the conditions you will use. Then use the oil viscosity that gives you 10 PSI per 1,000 RPM under those circumstances. For some reason very few people are able to get this simple principal correct. I cannot explain further.

These same rules apply to engines of any age, loose or tight. Just because your engine is old does not mean it needs a thicker oil. It will need a thicker oil only if it is overly worn, whether new or old. Yet the same principals of 10 PSI per 1,000 RPM still apply. In all cases you need to try different weight oils and see what happens. Then choose the correct viscosity.

I am using 0W-20 in my Ferrari 575 Maranello right now. It has over 5,000 miles on the clock. There will be a day (my estimate is 50,000 miles) when I will have to go to a 0W-30. In the future I will have to increase the viscosity to a 0W-40, then a 0W-50, maybe. I will use whatever it takes to give me 75 PSI at 6,000 RPM during the lifetime of my engine. This formula works in all situations.

Some people have tried this and occasionally get a somewhat low oil pressure while at idle. This is fine. There is no stress on parts at idle, the smallest oil flow will do the trick. It is at higher RPM where more BHP is produced. This is where we need the flow. Remember that Ferrari uses 75 PSI at 6,000 RPM as the place to test your oil viscosity needs. If your oil gives this value under your driving conditions then your lubrication system has been maximized. Period.

Do not go 5,000 miles with the same oil if you are racing your car. You should change the oil every 1 or 2,000 miles. If you drive your car around town then you need to change the oil for that situation. Use racing oil on the track and urban oil around town. The best situation as described by Ferrari is to use the 0W-40 around town and the 10W-60 “racing oil” on the track. It has to be that “hot” track though. A compromise situation would be to use the 5W-40 for both but this may not be optimal. Certainly, if you are just an urban driver as me use the 0W-40 or even a thinner oil as I do in my Maranello. Again, I use the 0W-20.

FYI. The Formula 1 cars that run at 15,000 RPM and higher use straight 5 and 10 weight oils.

Now let me discuss what people think is a similar situation to racing. That is hot summer traffic jam driving. Your car should be able to handle this. If you have problems then you have a problem with your car, most likely in need of a cooling system overhaul.

When you drive that car down the road mid-winter in upstate New York or mid-summer in Florida the engine and oil temperatures will be around 212 F. But your Florida vacation is suddenly altered by a hurricane. You have to get out of Tampa, but so do a million other people. It is now 95 F and you are in a snarl. Everyone thinks they need a thicker oil for this situation. This is false.

Your engine is not producing much heat at low RPM and low BHP output. The production of heat is relatively slow. It can easily be transmitted to your cooling system. The problem is that your cooling system has trouble getting rid of the heat. The oil and the coolant will slowly rise in temperature. They both rise together. The increase is no big deal for your oil. It goes to 220, then 230 F. The problem is that the cooling system can only handle heat up to 230 F. After that you overheat the cooling system and the car must be shut off. The oil never got that hot, It was just that the water got a little hotter than its system design.

You now see that overheating in traffic is a cooling system problem and not an oil system problem. Do not change to a thicker oil based on your traffic situation.

Motor Oil 106

Chapter Six.

A personal recommendation.

These are the motor oils I recommend. This is based on information that I just happened to collect. I have not gotten the specifications of all oils out there. My opinion on these oils is based on viscosities. By this I mean less honey like at start-up temperatures and appropriate for the required viscosity at operating temperature. I broke it down to two classes, 1-Fully Synthetic and 2-Mineral (dinosaur) oils and blends of dinosaur and synthetic. The asterisk is my preferred from each group of similar products. And these are usually easier to find in my experience. Remember, all oils are too thick at start-up. There is no such thing as an oil that is too thin below 100F. The thinnest motor oil made is still too thick at start up temperatures.

It seems that many engines work best with a multigrade 30 weight oil. Others would do better with a 40 weight oil and some would require a 20 weight oil. You can only determine what is best by experimenting. Admittedly I did not think my Ferrari Maranello would need a 20 weight oil. In truth I could actually use a 10 weight oil. A 0W-10 would be good but it simply does not exist for normal use. Red Line does make 2W, 5W and 10W oils (this acts as a 0W-10 multigrade oil) but they are for racing only. One Formula 1 team has actually used these very oils off the shelf from Red Line.

. Synthetic Class:

60 wt:
Redline straight 60 wt racing oil (racing only, acts as a SAE 20W-60 oil)
Shell Helix Ultra Racing Oil 10W-60
Valvoline SynPower 20W-50*

50 wt:
Castrol Syntec 5W-50*
Shell Helix Ultra 15W-50
Penn Synthetic 5W-50

40 wt:
Mobil 1, 0W-40*
Shell Helix Ultra 5W-50

30 wt:
Mobil 1, 0W-30*
Penn Synthetic 5W-30

20 wt:
Mobil 1, 0W-20*
Valvoline SynPower 5W-20

. Non-Synthetic and synthetic blends:

60 wt:
Castrol Syntec Blend 20W-50

50 wt:
None recommended - all relatively too thick at start up.

40 wt:
Penn regular Multigrade 10W-40
Valvoline Durablend 10W-40*

30 wt:
Penn regular Multigrade 5W-30*
Valvoline Durablend 5W-30

20 wt:
Penn regular Multigrade 5W-20*
Valvoline Durablend 5W-20

If while on the road you are forced to add oil there are rules. Let us say for example that our engine has synthetic Mobil One 0W-30.

Use the same type and brand if you can. If you are using Mobil 1 then it is acceptable to mix different grades but use a close grade when possible. It is not a good idea to mix say 1/2 your oil tank with 0W-30 and 1/2 with 15W-50 Mobil One.

If there is no Mobil 1 available then use mineral based oils next, preferably Mobil as first choice then any other name brand next.

The last choice is to mix a synthetic of another brand. They specifically said this should not be done in the past but most say that mixing is compatible now.

I personally use Mobil 1, 0W-20 in the 575 Maranello and for the first oil change I drained the Murcielago’s 5W-40 Agip and replaced it with 0W-30 Mobil 1. The engine became much quieter. A valve tappet noise disappeared. I may try the 0W-20 next. For all my other cars I use the regular Pennzoil Multigrade 5W-20.

You have to try by experimentation what operating oil grade your engine requires. In all cases however, you want the oil that gets least honey-like at startup.

Again, my choices based on oils I studied and giving the least thickening after engine shut-down.

Motor oil 107

Chapter Seven.

What is the terminology from SAE and API.

Many think that the “W” in 10W-30 means “winter”.
From SAE J300 p.2:
"Two series of viscosity grades are defined in Table (1): (a) those containing the letter W and (b) those without. Single viscosity grade oils with the letter W are defined by maximum low temperature cranking and pumping viscosities and a minimum kinematic viscosity at 100C. Single grade oils without the letter W are based on a set of minimum and maximum kinematic viscosities at 100C and a minimum high shear rate viscosity at 150C. The shear rate will depend on the test method. Multigrade grade oils are defined by both of these criteria....
The W is just a designation of one type of testing vs another. I personally asked them if it stood for "winter" and they flatly said "no".

What is the viscosity of the various weight oils? The definitions are as follows:

From SAE J300, viscosities at 212 F...

20, range - 5.6 to 9.2
30, 9.3 - 12.4
40, 12.5 - 16.2
50, 16.3 - 21.8
60, 21.9 - 26.1

By a modified analysis the min. viscosity at 302 F...

20, 2.6
30, 2.9
40, 2.9 - 3.7
50, 3.7
60, 3.7

Note again that the difference between the 20W and 60 weight oils at 302 F is only about 1 (one). Whereas the difference in viscosity at 104 F is 120 units. The 20W has a viscosity of 40 and the 60W a viscosity of 160. The difference at startup is even higher, probably 250 or 300.

The American Petroleum Institute, API, and Society of Automotive Engineers, SAE, have rated engine oil performance over the years. We have seen the ratings go from SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL with SM to follow. SI and SK were eliminated as they are used by other businesses. There are over 3 dozen tests that oil now must pass in order to make the next higher rating. The tests are defined by the American Society for Testing and Materials, ASTM. Some tests have progressed to a zero tolerance level. For example there can be no sticking of any piston rings any more. I will compare the SL rated oil to the previous SJ oil in a few categories. For simplicity I will skip the units of measurement:

.......S J........S L......

.......30........20......maximum cam plus lifter wear
........9.........7.8.....sludge build up
........5.........8.9.....varnish rating (more is better)
.......60.......45.......high temperature deposits
.......17.......10.......high temperature volatility

Other categories include: Resistance to rust, resistance to foaming, resistance to oil consumption, homogeneity and miscibility, flow reduction with varying amounts of absorbed moisture, gelation index and others.

As one can see just going from the previous SJ to the SL rating is a significant improvement. I cannot wait to get the upcoming SM oil into my cars.

Regarding cool whether gel formation, a small except from SAE j300 1999:
4. Because engine pumping, cranking and starting are all important at low temperatures the selection of an oil for winter operation should consider both the viscosity required for oil flow as well as cranking and starting, at the lowest expected ambient temperature.
Pumping viscosity is a measure of an oils ability to flow...during the initial stages of operation. Test in ASTM D 4684. ....samples are tested after a slow cool cycle. This cycle has predicted as failures several SAE 10W-30 and 10W-40 oils which are known to have suffered pumping failures in the field after short-term (2 days or less) cooling. These field failures are believed to be the result of the oil forming gel structures that result in excessive yield stress and viscosity of the engine oil...
A.2.1...After preliminary warming, the sample is subjected to a controlled temperature/time cycle over 5 1/2 to 7 days. The cycle reproduces ...instability or reversion which has occurred during storage of oils in moderately cold cyclic conditions. Recent work shows relevance to engine oil pumpability failure. Oils exhibiting pour reversion have solids resulting from wax gel formation, at temperatures significantly higher than their ASTM D 97 pour points.
Extracted, from ASTM D 4485-03 Standard Specification for Performance of Engine Oils, copyright ASTM International, 100 Barr Harbor Drive, Wets Conshohocken, PA 19428, USA.

My point is that tests are not just laboratory concoctions. They design tests to match real life conditions.

I use 5W-20 Pennzoil mineral based multigrade oil in my Expedition as it has many of the low temperature characteristics of higher weight synthetic oils. My '04 manual states that the SUV is delivered with a Ford semi-synthetic oil and although regular oil can be used they recommend a semi or full synthetic oil. For the differential gear oil they used 75W-140 in my ‘98 Expedition but now recommend 75W-90.

Please note that it makes no difference what oil you are using. The 0W-20 Mobil 1 that is SL rated meets the same criteria as that SL rated 10W-30 synthetic or mineral based Pennzoil. That SJ or in particular that SH oil some people are looking for (from their older automotive owners manual) is no where near as good as any SL oil of today. Always use the most currently available, highest rated motor oil, even in the oldest, most worn engine. You may require a thicker grade but just make sure it is SL rated.

The SH rating was used in oils starting 1993. The SJ rating started in 1997 while the SL became effective in 2001 oils. According to ASTM D 4485, SL rated oils are superior to previous oils and from:
X2.3.1 and 2: SL oil is for use in current and all earlier passenger cars, sport utility vehicles, vans, and light trucks. This SL rated oil can be used in engines requiring SJ and all earlier categories.

See: American Society for Testing and Materials- ASTM International
........Society of Automotive Engineers- SAE International
........American Petroleum Institute- Welcome To The API Website

Motor Oil 108

Chapter Eight.

Odds and ends.

I have some stories that I collected. First, my architect drives a big SUV. He was running with Mobil 1 brand 15W-50. He changed it to Pennzoil Multigrade (mineral oil based, non-synthetic, cheap) 5W-20 at my suggestion. His gas mileage went from 10 to 13 MPG around town. What really impressed him the most was the “robust” increase in “get up and go.” He changed from a thick synthetic to a thin mineral oil. His venue is stop and go city traffic in Florida, mostly short trips. The oil just never got that hot to require a 50 weight oil. Short trips means that the oil temperature never gets up to the normal operating range. It was too thick on short trips and too thick when it did get up to temperature.

The lower temperatures he was seeing occurred because of reduced friction and internal drag and higher oil flow.

One of the members of the Ferrari Chat web site went from a 40 to a 30 weight oil in his Ferrari 355 for racing in Texas. He noticed a drop in temperature but no change in oil pressure. This may seem odd but really makes perfect sense. Since the 30 weight oil is thinner he got better flow and therefore better cooling. The oil was at a lower temperature so it was not as thin than it would have been at the previous higher temperature. Cooler engines last longer. Fact: The higher the temperature, the greater the wear, all other things being equal.

People say that their old car manual says to use a 10W-40 so they would never think of using a 0W-40. Again, both are essentially the same viscosity at normal engine operating temperature. The 0W-40 just does not thicken as much after you turn off your engine. There are now several cases when manuals for older cars have been updated to reflect this. My 550 Ferrari Maranello manual said to use 5W-40 yet the 575 manual says to use the 0W-40. The engines are the same except the 575 has more BHP. It has better acceleration and more top speed. The engines have the same tolerances.

All manufacturers I have seen are specifying 0W-XX or 5W-XX oils now. Honda, Ferrari, Ford, Mercedes, Porsche, and others specify a 0 or 5W-XX oil to mention a few. These are appropriate for all engines of all ages of all levels of wear. This second number is the only thing that may change with an older, lose or worn engine. This can only be determined by experimentation. If you are using XW-50, go to a 0W-40. If your pressures are still too high go to a 0W-30 and so on.

When I took delivery of my 575 Maranello I drove for 500 miles then changed the oil to 0W-30 Mobil 1. There were no changes in operating pressure or temperature. Starting the engine seemed faster though. I called up FNA and was told that all new Ferrari cars are delivered with 5W-30 Shell Helix Ultra. That is when I decided to try the 0W-20 Mobil 1. I could even go to a 10 weight oil as my pressures are still excessive while driving around town. I do not drive on the track.

What about the break in period? For one thing you could just follow the car’s manual and gradually break your engine in. Some cars like Ferrari and Lamborghini run engines and the cars for a period of time before you even take delivery. They often run up to full power. Some representatives at least from Ferrari hinted that the traditional break in period was not really needed, at least in their car.

Most people who buy high powered cars that I have experienced will just get in there cars and step on the gas fully. They do not wait for the oil to warm up. Personally I would not mind running full BHP for short bursts during the break in period but I always fully warm up the engine first.

Older engines may in fact benefit from thinner oil use. Over time permanent deposits of carbon and sludge build up in the engine oil ways. It is like a clogging of arteries in humans. We are now all on blood thinners. This is an area I specifically studied while a general surgeon resident at Chapel Hill.

Thinner oils, and specifically synthetic products are better. Some people say their engines were “designed” to run on mineral based lubricates. I have not seen anything to support this theory. The synthetic of the same viscosity as the mineral oil you are now using will be an improvement. If you go from a mineral to an even thinner synthetic you may be better off still. The pressures go up in many older engines because of this “clogging” of the arteries. Most think this is good but it is really a lessening of flow and therefore accelerates engine wear even further.

For those engines with excessive varnish and carbon buildup the engine oil additives of the detergent type may be of benefit. On the other hand you could just use a thin synthetic oil and change it every 200 miles for a while and end up with an even cleaner engine. With everything working properly you may actually need a thicker oil if that engine is overly worn. The thicker oil would be a disaster however, if the arteries were narrowed from deposits.

Remember, the only difference between a 0W-40 and a 10W-40 is that the 0W-40 thickens less after you turn off your engine. It is still too thick in the morning at startup but not as thick as the 10W-40. Yet, they are still too thick to use until they both warm up to operating temperature at which point they have the save viscosity, around 13 to 14. Remember that the 0W-30, 10W-30 and straight 30 weight oils all have a viscosity of around 10 at normal engine operating temperatures.

There is one more thing. A 20 weight oil is not half as thick as a 40 weight oil. The real scale is more like the oils having an absolute thickness of 108 and 114. Now it can be seen that the 40 weight oil is only around 10 percent thicker than the 20 weight oil. The difference is not that much at operation but at startup the difference is significant. Pressure / flow dynamics go along with this 10 percent figure. A 30 weight oil should be thought of as having an absolute viscosity of 110 and a 50 weight oil has an absolute viscosity of 120. I am talking about operating temperatures.

I thought everyone knew that 90 percent of engine wear occurs during the startup period because oil is just too thick. Some think it is good to have a thicker oil for startup since the parts shrink when cold and would otherwise “rattle.” Sure, your piston diameter will shrink on cooling but so will the diameter of your bore. The net result is about the same clearance hot and cold. This is not true for your valves. They lengthen when extremely hot. In the Murcielago they use shims instead of self adjusting valve tappets. You need to put a millimeter of clearance there so that after expansion the valve will not be held partly open when it is supposed to be closed.

It it were true that thicker oils were needed at startup then the manufacturers would not be requesting oils that thicken less on cooling. They would just specify that one should use a straight 30 or 40 weight oil. Instead, over time, they are specifying thinner and thinner oils.

The manufacturers know what parts shrink or expand and the clearance changes that result. You do not have to worry about this. If it was that easy to design engines we would all be making them.

I would like to go back to the worry that oil falls off the parts when a car is stored or sees long periods of inactivity. For the first oil change in my 575 Maranello I drained the Shell and put in 0W-30 Mobil 1. This was at 775 miles on the odometer. I drove the car home from work, put it on the lift and drained the transaxle and engine oils. I also opened and drained the oil cooler and took off every line that is in the oil system. I wanted to get every speck of the Shell oil out of there. For optimal results you are not supposed to mix synthetic oils of different brands.

The system takes 12 quarts with a “normal” oil change but took 15 quarts for this change. It all took about an hour. I then started the engine to check for leaks. The multitude of mechanical engine noises that followed nearly broke my eardrums for about 10 long seconds. Then it was suddenly very quiet. You could hear a pin drop. There was certainly the most possible amount of surface oil on all the internal parts as the engine was only off for an hour. But it was not until the oil circuit primed, filled then sent flow into all the parts that any lubrication was occurring. Hence all oil filters that are manufacturer certified have back flow limiters to keep the oil filter full even with the engine off.

Here is an interesting tidbit of information. A 75W-90 gear oil has the same viscosity as a 10W-40 engine oil at 212 and 302 F. Once again, those numbers on that oil can are misleading and certainly add to the confusion I see among automotive enthusiasts.

Motor Oil 109

Chapter nine.

Let’s start over.

We have seen that 0W-30, 5W-30, 10W-30 and straight 30 weight oils all have the exact same viscosity at 212 and 302 F. What about startup viscosities? Do 0W-20, 0W-30 , and 0W-40 all have the same viscosity at a 75 F startup. The answer is no. The SAE J300 standard allows for this discrepancy. Here are some examples:

..Viscosity at 75 F startup..


The numbers are not exact but they show clearly that the ”0” represents different startup viscosities. This is unlike the 0W-30, 5W-30, 10W-30 and straight 30 weight oils that all have the exact same viscosity in a hot engine = 10 cS.

I would like to comment on the following statements made by a knowledgeable automotive enthusiast:
“Pressure and flow are tied together with viscosity, but none have anything to do with lubrication. Lubrication is a property of the fluid, not the force. The oil pump would pump water just as well, but it would offer no real lubrication. If we double the pressure, we double the flow. If you decrease the viscosity to a lighter oil, you increase flow at a loss of pressure. High flow helps to carry away more heat. High pressure helps to keep metal parts like the bearings out of contact with each other (scuffing).”

I give you the following example to help visualize what is happening. This assumes the oil has no internal resistance. In actuality doubling the pressure will not double the flow but will be slightly less. And thicker oils have more resistance than thinner oils for all situations. But simplified we get the following:

For a 30 wt oil at operating temperature:
1,000......20 PSI....1
2,000......40 PSI....2
4,000......80 PSI....4
8,000... 160 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 5

For a 30 wt oil at operating temperature
and a higher output oil pump:
1,000......30 PSI....1.5
2,000......60 PSI....3
4,000....120 PSI....6 The maximum flow because of the oil pop off valve at 90 PSI will be 5
8,000... 240 PSI....12

If we stick with the same weight oil and increase the oil pump output we will increase the pressure and the oil flow too. If we double the oil pump output we will double the pressure and we will double the oil flow (in an ideal system).
1,000......40 PSI....2
2,000......80 PSI....4
4,000....160 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 5
8,000... 320 PSI....16

Let us compare a 40 wt oil at operating temperature:
The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow.
1,000......30 PSI....1
2,000......60 PSI....2
4,000....120 PSI....4 The maximum flow because of the oil pop off valve at 90 PSI will be 3
8,000....240 PSI....8

For a 40 wt oil at operating temperature
and a higher output oil pump:
1,000......45 PSI....1.5
2,000......90 PSI....3 The maximum flow because of the oil pop off valve at 90 PSI will be 3
4,000....180 PSI....6
8,000... 360 PSI....12

For a 40 wt oil at operating temperature
with the original pressures:
1,000......20 PSI....0.5
2,000......40 PSI....1
4,000......80 PSI....2
8,000... 160 PSI....4 The maximum flow because of the oil pop off valve at 90 PSI will be 3

Increasing the pressure while using the same oil will increase the oil flow but increasing the pressure by increasing the oil thickness will result in less flow. It takes more pressure to move a thicker oil. When you go to a thicker oil the pressure goes up because of the increased resistance, and therefore reduction of flow.

There is more to these graphs but I will contiue with the next chapter.

Furthermore pressure does not equal lubrication. Let us look at a single closed “lifetime lubricated” bearing. We could hook up a system to pressurize the bearing. This can actually be done. We could have the oil at ambient pressure. We could then double, triple, quadruple the pressure of the oil. The oil is non-compressible. Regardless of the pressure we would have the exact same lubrication, that of the ambient pressure lubrication.

The physics of lubrication as I said earlier show a 1:1 relationship of flow to separation pressure. Lubrication itself is pressure independent. I will not go into the mathematical equations for this.

Even water can be used as a lubricant. This is partly because of its high surface tension. It is used in many medical devices and other systems that are under or exposed to water. It is just that water rusts metal parts making this unsuitable for automotive engines. It actually has a higher specific heat than oil. It can therefore carry away more heat than oil from bearing surfaces. In this respect water is a better lubricant than oil.

Motor Oil 201

Chapter 10.

The graduate.

I am going to bring up the constant flow pump concept. First, it goes back to the principal that doubling the pressure of the same weight oil does not exactly double the flow but it is close. Also doubling the RPM for the same reason does not exactly double the flow but again it is close.

This shows the problem best:

(A) For a 30 wt oil at operating temperature:
1,000......20 PSI....1
2,000......40 PSI....2
4,000......80 PSI....4
8,000... 160 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 5

(B) For a 30 wt oil at operating temperature
and a higher output oil pump:
1,000......30 PSI....1.5
2,000......60 PSI....3
4,000....120 PSI....6 The maximum flow because of the oil pop off valve at 90 PSI will be 5
8,000... 240 PSI....12

If we stick with the same weight oil and increase the oil pump output we will increase the pressure and the oil flow too. If we double the oil pump output we will double the pressure and we will double the oil flow.

(C) For a 40 wt oil at operating temperature:
The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow. Compare this with (A):
1,000......30 PSI....1
2,000......60 PSI....2
4,000....120 PSI....4 The maximum flow because of the oil pop off valve at 90 PSI will be 3
8,000....240 PSI....8

(D) For a 40 wt oil at operating temperature
and a higher output oil pump:
1,000......45 PSI....1.5
2,000......90 PSI....3 The maximum flow because of the oil pop off valve at 90 PSI will be 3
4,000....180 PSI....6
8,000... 360 PSI....12

The situations (A) and (C) are close to real life, assuming no loss in the system. This is what happens when you change the 30 weight oil to a 40 weight oil in your car:

(A) For a 30 wt oil at operating temperature:
1,000......20 PSI....1
2,000......40 PSI....2
4,000......80 PSI....4
8,000... 160 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 5

(C) For a 40 wt oil at operating temperature:
The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow.
1,000......30 PSI....1
2,000......60 PSI....2
4,000....120 PSI....4 The maximum flow because of the oil pop off valve at 90 PSI will be 3
8,000....240 PSI....8

At 6,000 RPM the maximum rate of flow has been reached with the thinner oil (A). When you go to 7, 8 or 9,000 RPM you do not get any more flow. You only get a maximum rate of 5. The internal forces on the bearings increase but there is no additional flow of oil.

With the thicker oil you reach maximum flow at 3,000 RPM (C). Worse yet is that the maximum flow is now only 3. As we increase RPM to 4, 5, 6, 7, 8, 9,000 RPM we get no additional pressure and no additional flow, no increase in lubrication.

Next let us look at a 20 weight oil at operating temperature. We get the same flow out of our constant volume pump but the thinner oil requires less pressure to move through the system. This even goes along with the rule that we should use an oil that gives us 10 PSI per 1,000 RPM:

(D) RPM....Pressure..Flow
1,000......10 PSI....1
2,000......20 PSI....2
4,000......40 PSI....4
8,000.. ...80 PSI....8

The maximum flow rate has not been reached. If the engine went to 9,000 RPM then the flow would be 9 at 90 PSI, our maximum pressure at pop off. The engine now has 3 times the flow rate as with the 40 weight oil at full RPM. The nozzles at the bottom of each cylinder are spraying 3 times the amount of oil lubricating and cooling this section. Everything runs cooler and the separation forces in the bearings are 3 times higher.

For engines that redline at 5,000 RPM they usually pop off the oil pressure at 50 to 60 PSI. For engines that go to 8-9,000 RPM the pressures max out at 90-100 PSI. You can now see that you can only get the maximum flow rate if you follow the 10 PSI / 1,000 RPM rule.

The winner: 0W-20 weight oil for my Maranello. I said earlier that I could use a 10 weight oil. I actually only run with 185 F oil temperature around town and the pressures are similar to the 40 weight oil example in (C) above. This is why I also said that in the racetrack condition, with hotter, thinner (0W-20) oil I may actually get the optimal results as in (D) above.

Now let us go back to the Ferrari recommended parameters in my 575 Maranello manual. It calls for 75 PSI at 6,000 RPM. The pop off pressure has not been reached. As we now increase the RPM we still get an increase in flow rate. This is what we need and this is exactly what they are recommending. We get our maximum flow at the maximum system pressure, at about the maximum engine RPM of 7,700. There is no bypassing of the oil. All oil pumped goes through the system. There is no wasted BHP pumping oil past the bypass valve back to the oil tank. It is the perfect system.

Finally I will compare a single, 30 weight oil, at normal (212 F) and at racetrack (302 F) temperatures:

(A) For a 30 wt oil at normal (212 F) operating temperature:
1,000......20 PSI....1
2,000......40 PSI....2
4,000......80 PSI....4
8,000... 160 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 5

(E) For a 30 wt oil at elevated (302 F) operating temperature. The oil is thinner at 302 F. It requires less pressure to get the same flow:
1,000......10 PSI....1
2,000......20 PSI....2
4,000......40 PSI....4
8,000......80 PSI....8 The maximum flow because of the oil pop off valve at 90 PSI will be 9

The hotter (302 F) 30 weight oil is thinner than the cooler (212 F) 30 weight oil. It has the same flow rate in the constant volume oil pump but at a lower pressure than the oil at normal operating temperature. This allows for a doubling of the flow rate at peak RPM. The thinning of oil at higher temperatures is a benefit. You get more flow, more cooling and more lubrication.

The 30 weight oil at 302 F has the exact same flow rate and pressures as the 20 weight oil at 212 F. See (D) above. Therefore, use the 20 weight for around town driving and the 30 weight on the hot track. You get maximum flow at each situation.

For YOUR engine, substitute the actual flow at 1,000 RPM. If your engine puts out 1.5 liters/min. at 1,000 RPM it would put out 3 liters/min. at 2,000 RPM and 6 liters/min. at 4,000 RPM and so on. The maximum flow in (A) would be 7.5 liters/min. In situations (D) and (E) you would get a maximum of 13.5 liters/min.

The reason that multigrade oils were developed in the first place was to address the problem of oil thickening after engine shutdown. Over the years we have been able to reduce the amount of thickening that occurs. Never-the-less there is no oil that does not thicken after you turn your engine off. This is why we have to warm up our engines before revving them up. Engine designers always pick the recommended oil based on a hot engine and hot oil. There is no issue with oil thinning as they are both matched when hot. The problem is oil thickening when the engine cools.

Cold engine showing very high pressures because of the thickened oil at startup:

For a 40 wt oil at 75 F at startup:
The oil is thicker, has more internal resistance and therefore requires more pressure to get the same flow.
1,000......60 PSI....1
2,000....120 PSI....2 The maximum flow because of the oil pop off valve at 90 PSI will be 1.5
4,000....240 PSI....4
8,000....480 PSI....8

At 1,500 RPM you reach the maximum oil flow rate and if you run to 8,000 RPM it is the same rate. The flow cannot increase and it is insufficient. This is why we must wait until our oil temperature comes up to 212 F or higher. The maximum flow rate in this case will then double, up to 3. To get even more flow in our test engine you need to use a lower viscosity grade.

If you have absorbed and digested the information here you should be able to pick out the proper operating oil weight for your car, be it a 30, 40, 50 or even 20 weight oil. I have always used oils that were a grade thinner than recommended even though many use a grade thicker than recommended. I showed evidence that the starting grade should always be 0 or 5 (0W-XX or 5W-XX for thicker oils). If you want the best protection and highest output from your motor use a synthetic based oil. The actual brand is not as critical as the viscosity. The rating must be SL or the upcoming SM rating. Change your oil every 3 - 5,000 miles and at least every spring.

Final examination to follow later.


Hates Electrical
1,164 Posts
I was reading up on Oil recently and I thought that this article would be a great addition to the very thorough, yet also very technical article quoted above by Sam.


How much do you value the engine in your car? Think about it, because the life of your engine depends in no small part on the quality of the oil you put in it - oil is the lifeblood of your car's engine. From the mid 80's for 8 or 9 years there was a veritable revolution in car engine oil. All oils were no longer the same thanks to the popularity of hot hatches, 16-valve engines and turbos as the tuner scene started to rise. Combined with the devastating problems of black death, the days of one oil catering for everyone were over.
Take Castrol for example. They led the field for years with GTX. This was surpassed a few years back by semi-synthetic and fully synthetic oils, including GTX2 and GTX3 Lightec. Now, that's been surpassed by Formula SLX which can cost upwards of £50 ($75) for 5 litres. And most recently, Castrol GTX Magnatec which is muscling in on the hitherto separate world of friction reducers (and we'll deal with them later, on the additives page.).

What does my oil actually do?
An engine oil's job is primarily to stop all the metal surfaces in your engine from grinding together and tearing themselves apart from friction whilst transferring heat away from the combustion cycle. Engine oil must also be able to hold all the nasty by-products of combustion, such as silica (silicon oxide) and acids in suspension. It cleans the engine of these chemicals and build-ups, and keeps the moving parts coated in oil. Finally, engine oil minimises the exposure to oxygen and thus oxidation at higher temperatures. It does all of these things under tremendous heat and pressure.

What the heck was Black Death?
Black Death first appeared in the early 80's when a horrible sticky black substance was found to be the cause of many engine seizures in Europe. Many engines were affected but Ford and Vauxhall (GM) suffered the most. Faster roads, higher under-hood temperatures, tighter engineering tolerances and overworked engine oils turned out to be contributors to the problem. The oils just couldn't handle it and changed their chemical makeup under pressure into a sort of tar-like glue. This blocked all the oil channels in the engines, starved them of lubrication and caused them to seize. I don't recommend this but you can reproduce the effect with a frying pan, cooking oil and a blowtorch. The cooking oil will heat up far quicker than it's designed to and will turn to a sticky black tar in your pan. Either that or it will set fire to your kitchen, which is why I said "don't do this".
Anyway, burning kitchens aside, Black Death was the catalyst for the production of newer higher quality oils, many of them man-made rather than mineral-based.

Black death for the 21st century

There's a snappy new moniker for Black Death now, and it's called sludge. The cause is the same as Black Death and it seems to be regardless of maintenance or mileage. The chemical compounds in engine oils break down over time due to prolonged exposure to high temperatures and poor maintenance habits. When the oil oxidises, the additives separate from the oil and begin to chemically break down and solidify, leading to the baked-on oil deposits turning gelatinous, and that nasty compound is what is lovingly referred to nowadays as sludge. It's like black yoghurt. What doesn't help is that modern engines, due to packaging, have smaller sumps than in the "good old days" and so hold less oil. This means that the oil that is present in the engine can't hold as much crap (for want of a better word) and can lead to earlier chemical breakdown.
The most common factor in sludge buildup is mineral oils combined with a lack of maintenance by the car owner combined with harsh driving conditions. But this isn't true in all cases. For some reason, a 2005 Consumer Reports article discovered that some engines from Audi, Chrysler, Saab, Toyota, and Volkswagen appear prone to sludge almost no matter how often the oil is changed.

What does sludge look like?
I was contacted by a BMW driver who's been having a particularly harsh time with sludge and has been discussing it on the Bimmerfest forums. He posted some images of his problem and other readers posted similarly-framed images of the same engine components in "normal" condition. Below are two of those photos. On the left is what the cam case should look like in a well maintained engine when photographed through the oil filler cap. On the right is what the same type of engine looks like when suffering sludge buildup.

In this example, the consensus was that the sludge buildup was caused by an overheating engine, oil that hadn't been changed for 20,000 miles of stop-go city driving, a lot of cold starts and a period of about 12 months in storage without an oil change. Most of this happened before the current owner got it.

Curing sludge
There are no hard and fast rules for curing an engine of sludge buildup. If it's really bad, flushing the engine might be the only cure, but that could also cause even more problems. If flushing the engine results in bits of sludge getting lodged where they can do more damage, you're actually worse off.
It's interesting to note that some race techs have reported sludge buildup in race engines as a result of aftermarket additives being used in conjunction with the regular oil. The chemical composition of the additives isn't as neutral as some companies would lead us to believe, and combined with particular types of oil and high-stress driving, they can cause oil breakdown and sludge to appear. The lesson from them appears to be "don't use additives".

When is sludge not sludge?
Easy. When it's an oil and water emulsion from a leaking or blown head gasket. If this happens, you get a whitish cream coloured sludge on the inside of the oil filler cap. The filler cap is typically cooler than the rest of the cam case and so the oil/water mix tends to condense there. So if you take the oil filler cap off and it looks like it's covered in vanilla yoghurt or mayonnaise, you've got a blown head gasket. A surefire way to confirm this is if your oil level is going up and your coolant level is going down. The coolant is getting through the breaks in the head gasket and mixing with the oil. When it gets to the sump it separates out and the oil floats on top. A slightly more accurate way to check for this condition is to use a combustion leak tester, or block tester. If you're in America, NAPA sell them for about $45 (part #BK 7001006). If you're in England, Sealey sell them for about £70 (model number VS0061). Combustion leak testers are basically a turkey baster filled with PH liquid, with a non-return valve at the bottom. To use one, run your engine for a few minutes until its warm (not hot) then turn it off. Use a protective glove (like an oven glove) and take the radiator or reservoir cap off. Plug the bottom of the combustion leak tester into the hole and squeeze the rubber bulb on top. It will suck air from the top of the coolant through the non-return valve and bubble it through the PH liquid. If the liquid changes colour (normally blue to yellow), it means there is combustion gas in the coolant, which means a head gasket leak.
There is one other possible cause for this yellow goop : a blocked scavenger hose. Most engines have a hose which comes off the cam cover and returns to the engine block somewhere via a vacuum line. This is the scavenger hose which scavenges oil vapour and gasses that build up in the cam cover. If it's blocked you can end up with a buildup of condensation inside the cam cover, which can manifest itself as the yellow goop inside the filler cap.

VW / Audi sludge problems
While the the 1.8T engines in Audi A4's, Audi TT, VW Passat, Jetta, Golf, New Bettle, are all very prone to sludge build-up, Audi/VW does not have an extended warranty for them from the factory. The factory warranty is 4 year/50,000 miles but it can be extended if purchased.
Although Audi/VW now has 10,000 mile service intervals, oil changes can be done between "services", and should be done if the vehicle is driven in heavy traffic, offroad, and non-highway use. Also, Audi/ VW will only warrant an engine if the customer has proof of all their oil changes. As of 2004 I belive all 1.8T engines must use synthetic oil.
So if you own one of these sludge-prone engines, what can you do? Obviously, Volkswagen Audi Group (VAG) recommends that you use only VW/AUDI recommended oil which at the time of writing is Castrol Syntec 5W-40. You should also keep up on your oil changes, making them more frequent if you drive hard or haul a lot of cargo. The most important thing for the VW or Audi owner is this: if the oil light comes on and beeps the high pitch beep that most everyone ignores, pull over and shut the engine down immediately. Many VAG engines can be saved by this procedure. Have the vehicled towed to a VAG dealer. Their standard procedure is to inspect the cam bearings; if they're not scored, the oil pan will be removed and cleaned out and all the crankcase breather hoses and the oil pickup tube will be replaced. They'll do an oil pressure test with a mechanical gauge, and hopefully will also replace the turbo lines. Finally, the turbo will be checked for bearing free-play. The VAG turbos run really hot even with proper oil and coolant supply - that's why you need a good quality synthetic in them.

Toyota sludge problems
For their part, Toyota have the dubious honour of having the most complaints about sludge buildup in their engines - 3,400 at the last count. At the time of writing there is a class action suit going on against them. Details can be found at Toyota/Lexus Class Action Settlement-Official Court Website

Saab sludge problems
For an example of sludge in a Saab 9 5 Aero with only 42,000 miles on it, you might be interested to read my case study on this engine, put together with the help of a reader. Our sludge case study.

Mineral or synthetic?
Mineral oils are based on oil that comes from dear old Mother Earth which has been refined. Synthetic oils are entirely concocted by chemists wearing white lab coats in oil company laboratories. For more info, see the section on synthetics further down the page. The only other type is semi-synthetic, sometimes called premium, which is a blend of the two. It is safe to mix the different types, but it's wiser to switch completely to a new type rather than mixing.

Despite their name, most synthetic derived motor oils (ie Mobil 1, Castrol Formula RS etc ) are actually derived from mineral oils - they are mostly Polyalphaolifins and these come from the purest part of the mineral oil refraction process, the gas. PAO oils will mix with normal mineral oils which means Joe public can add synthetic to his mineral, or mineral to his synthetic without his car engine seizing up. (In truth, Mobil 1 is actually made by reformulating ethanol).
The most stable bases are polyol-ester (not polyester, you fool). When I say 'stable' I mean 'less likely to react adversely with other compounds.' Synthetic oil bases tend not to contain reactive carbon atoms for this reason. Reactive carbon has a tendency to combine with oxygen creating an acid. As you can imagine, in an oil, this would be A Bad Thing. So think of synthetic oils as custom-built oils. They're designed to do the job efficiently but without any of the excess baggage that can accompany mineral based oils.

Pure synthetics
Pure synthetic oils (polyalkyleneglycol) are the types used almost exclusively within the industrial sector in polyglycol gearbox oils for heavily loaded gearboxes. These are typically concocted by intelligent blokes in white lab coats. These chaps break apart the molecules that make up a variety of substances, like vegetable and animal oils, and then recombine the individual atoms that make up those molecules to build new, synthetic molecules. This process allows the chemists to actually "fine tune" the molecules as they build them. Clever stuff. But Polyglycols don't mix with normal mineral oils.

While we're on synthetic oils, I should mention Amsoil. I originally had them down as an additive. I was wrong. I've got to say I've had no experience of the product myself so I can't vent my spleen about it. However, there is a particularly good page with a ton of info about it here. I recommend you pop over and read this and see what you think.
I've been contacted by Amsoil themselves and asked to point out the following:
Amsoil do NOT produce or market oil additives and do not wish to be associated with oil additives. They are a formulator of synthetic lubricants for automotive and industrial applications and have been in business for 30+ years. They are not a half-hour infomercial or fly-by-night product, nor have they ever been involved in a legal suit regarding their product claims in that 30+ year span. Many Amsoil products are API certified, and ALL of our products meet and in most cases exceed the specifications of ILSAC, AGMA etc..... Their lubricants also exceed manufacturers specifications and Amsoil are on many manufacturers approval lists. They base their claims on ASTM certified tests and are very open to anyone, with nothing to hide.

It turns out that Amsoil actually have the stance that they recommend engine oil additives are NOT to be used with their products. This will become relevant later on this page, and in the additives section. They have a pretty good FAQ on the Amsoil website, which you can find here.

Mixing Mineral and Synthetic oils - the old and busted concepts
For the longest time, I had this to say about mixing mineral and synthetic oils:

If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. I learned this lesson the hard way! It's wise to use a flushing oil first.
If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration.
Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.
Mixing Mineral and Synthetic oils - the new hotness
That's the thing with progress - stuff becomes out-of-date. Fortunately for you, dear reader, the web is a great place to keep things up-to-date, so here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website.
There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synetics. Polyglycols don't mix with normal mineral oils.)
There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.
There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.

Flushing oils
These are special compound oils that are very, very thin. They almost have the consistency of tap water when cold as well as hot. Typically they are 0W/20 oils. Don't ever drive with these oils in the engine - it won't last. (Caveat : some hybrid vehicles now require 0W20, so if you're a hybrid driver, check your owner's manual). Their purpose is for cleaning out all the gunk which builds up inside an engine. Note that Mobil1 0W40 is okay, because the '40' denotes that it's actually thick enough at temperature to work. 0W20 just doesn't get that viscous! To use them, drain your engine of all it's oil, but leave the old oil filter in place. Next fill it up with flushing oil and run it at a fast idle for about 20 minutes. Finally, drain all this off (and marvel at the crap that comes out with it), replace the oil filter, refill with a good synthetic oil and voila! Clean engine.
Of course, like most things nowadays, there's a condition attached when using flushing oils. In an old engine you really don't want to remove all the deposits. Some of these deposits help seal rings, lifters and even some of the flanges between the heads, covers, pan and the block, where the gaskets are thin. I have heard of engines with over 280,000km that worked fine, but when flushed it failed in a month because the blow-by past the scraper ring(now really clean)contaminated the oil and screwed the rod bearings.

Using Diesel oil for flushing
A question came up some time ago about using diesel-rated oils to flush out petrol engines. The idea was that because of the higher detergent levels in diesel engine oil, it might be a good cleaner / flusher for a non-diesel engine. Well most of the diesel oil specification oils can be used in old petrol engines for cleaning, but you want to use a low specification oil to ensure that you do not over clean your engine and lose compression for example. Generally speaking, an SAE 15W/40 diesel engine oil for about 500 miles might do the trick.

The question of phosphorus.
Phosphorus is the key component for valve train protection in an engine, and 1600ppm (parts per million) used to be the standard for phosphorus in engine oil. In 1996 that was dropped to 800ppm and then more recently to 400ppm - a quarter of the original spec. Valvetrains and their components are not especially cheap to replace and this drop in phosphorus content has been a problem for many engines. So why was the level dropped? Money. Next to lead, it's the second most destructive substance to shove through a catalytic converter. The US government mandated a 150,000 mile liftime on catalytic converters and the quickest way to do that was to drop phosphorous levels and bugger the valvetrain problem. Literally.
In the US, Mobil 1 originally came out with the 0W40 as a 'European Formula' as it was always above 1000 ppm. This initially got them out of the 1996 800ppm jam and knowledgeable consumers sought it out for obvious reasons. Their 15W50 has also maintained a very high level of phosphorus and all of the extended life Mobil synthetics now have at least 1000ppm. How do they get away with this? They're not classified as energy/fuel conserving oils and thus do not interfere with the precious government CAFE (corporate average fuel economy) ratings. (See my section on the EPA and fuel economy in the Fuel and Engine Bible for more info on this). This also means that they don't get the coveted ratings of other oils but they do protect your valvetrain.

A quick guide to the different grades of oil.
Fully Synthetic Characteristics
5W-40 Fuel economy savings
Enhances engine performance and power
Ensures engine is protected from wear and deposit build-up
Ensures good cold starting and quick circulation in freezing temperatures
Gets to moving parts of the engine quickly
Semi-synthetic Characteristics
15W-40 Better protection
Good protection within the first 10 minutes after starting out
Roughly three times better at reducing engine wear
Increased oil change intervals - don't need to change it quite so often
Mineral Characteristics
15W-40 Basic protection for a variety of engines
Oil needs to be changed more often

So what should I buy?
Quality Counts! It doesn't matter what sort of fancy marketing goes into an engine oil, how many naked babes smear it all over their bodies, how bright and colourful the packaging is, it's what's written on the packaging which counts. Specifications and approvals are everything. There are two established testing bodies. The API (American Petroleum Institute), and the European counterpart, the ACEA (Association des Constructeurs Europeens d'Automobiles - which was the CCMC). You've probably never heard of either of them, but their stamp of approval will be seen on the side of every reputable can of engine oil.

The API classifications are different for petrol and diesel engines:
For petrol, listings start with 'S' (meaning Service category, but you can also think of it as Spark-plug ignition), followed by another code to denote standard. 'SM' is the current top grade, which recently replaced 'SL' and 'SH'. 'SH' will be found on most expensive oils, and almost all the new synthetics. It's basically an upgraded 'SG' oil which has been tested more sternly.
For diesel oils, the first letter is 'C' (meaning Commercial category, but you can also think of it as Compression ignition). 'CH' is the highest grade at the moment, (technically CH-4 for heavy-duty) but 'CF' is the most popular and is well adequate for passenger vehicle applications.
Note about Castrol oils: Castrol have recently upgraded all their oils and for some reason, Castrol diesels now use the 'S' rating, thus completely negating my little aid-memoir above. So the older CC,CD,CE and CF ratings no longer exist, but have been replaced by an 'SH' grade diesel oil. This link is a service bulletin from Castrol themselves, explaining the situation.
The ACEA standards are prefixed with a 'G' for petrol engines and a 'D' or 'PD' for diesel. Coupled with this are numerous approvals by car manufacturers which many oil containers sport with pride. ACEA replaced CCMC in 1996 primarily to allow for greater read-across in test programs (eg. for viscosity, viscosity modifiers and base oil). The CCMC specifications were G (1 to 5) for gasoline, D (1 to 5) or heavy duty diesel and PD1 and PD2 for passenger car diesel. ACEA though have a slightly different nomenclature they can be summarised as A for petrol, B for passenger car diesel and E for heavy duty diesel. The ACEA grades may also be followed by the year of issue which will be either '96, '98 (current) but coming soon is 2000.
Full ACEA specs are:

A1 Fuel Economy Petrol
A2 Standard performance level
A3 High performance and / or extended drain
B1 Fuel Economy diesel
B2 Standard performance level
B3 High performance and / or extended drain
B4 For direct injection passenger car diesel engines
E1 Non-turbo charged light duty diesel
E2 Standard performance level
E3 High performance extended drain
E4 Higher performance and longer extended drain
E5 (1999) High performance / long drain plus American/API performances. - This is ACEAs first attempt at a global spec.
Typically, these markings will be found in a statement similar to: Meets the requirements of API SH/CD along the label somewhere. Also, you ought to be able to see the API Service Symbol somewhere on the packaging:

Beware the fake API symbol
Some unscrupulous manufacturers (and there's not many left that do this) will put a symbol on their packaging designed to look like the API symbol without actually being the API symbol. They do this in an effort to pump up the 'quality' of their product by relying on people not really knowing exactly what the proper API symbol should look like. To the left is an example of a fake symbol - it looks similar but as long as you remember what to look for, you won't get taken by this scam.
Amsoil are one of the biggest inadvertent offenders of the fake API symbol. Take a look at one of their labels here on the right. See that little starburst that says "Fuel efficient formula SL-CF"? It can say all it likes, but the fact of the matter is that this is absolutely not an API-certified SL or CF oil. That doesn't mean it doesn't perform to those levels, but for warranty purposes, this is not an API certified product. To be fair, some Amsoil products are API certified and they do have the correct labelling, but their top-tier products do not. The issue of fake API labelling and non-compliance has caused such a stir at Amsoil that they had to put an entire page up on their site dedicated to answering this particular question. You can find it here. Basically what it boils down to is money. Amsoil don't want to pay the $300,000 it can cost for an API certification of a single oil formulation, and getting API certification can limit them to single vendors for some of the raw products they use. If those vendors put their prices up or go out of business, Amsoil need to either pass the increase in price on to the consumer, or go through the whole API thing again from scratch.

If this is all confusing you, then rest assured that all top oils safely conform to the current standards. What you should treat with caution are the real cheapies and those with nothing but a maker's name on the pack. Anything below about £12 ($18) for 5 litres just isn't going to be worth it.

A Brief History of Time API ratings
Some people have asked about the old standards, and although they're not especially relevant, some rampant plagiarism from an API service bulletin means I can bring you all the API ratings right back from when the earth was cooling.

Petrol Engines Diesel Engines
Category Status Service Category Status Service
CJ-4 Current Introduced in 2006 for high-speed four-stroke engines. Designed to meet 2007 on-highway exhaust emission standards. CJ-4 oils are compounded for use in all applications with diesel fuels ranging in sulphur content up to 500ppm (0.05% by weight). However, use of these oils with greater than 15ppm sulfur fuel may impact exhaust aftertreatment system durability and/or oil drain intervals. CJ-4 oils are effective at sustaining emission control system durability where particulate filters and other advanced aftertreatment systems are used. CJ-4 oils exceed the performance criteria of CF-4, CG-4, CH-4 and CI-4.
CI-4 Current Introduced in 2002 for high-speed four-stroke engines. Designed to meet 2004 exhaust emission standards implemented in 2002. CI-4 oils are formulated to sustain engine durability where exhaust gas recirculation (EGR) is used and are intented for use with diesel fuels ranging in sulphur content up to 0.5% weight. Can be used in place of CD, CE, CF-4, CG-4 and CH-4
SM Current For all automotive engines presently in use. Introduced in the API service symbol in November 2004 CH-4 Current Introduced in 1998 for high-speed four-stroke engines. CH-4 oils are specifically designed for use with diesel fuels ranging in sulphur content up to 0.5% weight. Can be used in place of CD, CE, CF-4 and CG-4.
SL Current For all automotive engines presently in use. Introduced in the API service symbol in 1998 CG-4 Current Introduced in 1995 for high-speed four-stroke engines. CG-4 oils are specifically designed for use with diesel fuels ranging in sulphur content less than 0.5% weight. CG-4 oil needs to be used for engines meeting 1994 emission standards. Can be used in place of CD, CE and CF-4.
SJ Still current but nearly obsolete For all automotive engines presently in use. Introduced in the API service symbol in 1996 CF-4 Current Introduced in 1990 for high-speed four-stroke naturally aspirated and turbo engines. Can be used in place of CD and CE.
SH Obsolete For model year 1996 and older engines. CF-2 Current Introduced in 1994 for severe duty, two stroke motorcycle engines. Can be used in place of CD-II.
SG Obsolete For model year 1993 and older engines. CF Current Introduced in 1994 for off-road, indirect-injected and other diesel engines including those using fuel over0.5% weight sulphur. Can be used in place of CD.
SF Obsolete For model year 1988 and older engines. CE Obsolete Introduced in 1987 for high-speed four-stroke naturally aspirated and turbo engines. Can be used in place of CC and CD.
SE Obsolete For model year 1979 and older engines. CD-II Obsolete Introduced in 1987 for two-stroke motorcycle engines.
SD Obsolete For model year 1971 and older engines. CD Obsolete Introduced in 1955 for certain naturally aspirated and turbo engines.
SC Obsolete For model year 1967 and older engines. CC Obsolete Introduced in 1961 for all diesels.
SB Obsolete For older engines. Use this only when specifically recommended by the manufacturer. CB Obsolete Introduced in 1949 for moderate-duty engines.
SA Obsolete For much older engines with no performance requirement. Use this only when specifically recommended by the manufacturer. CA Obsolete Introduced in 1940 for light-duty engines.

Grade counts too!The API/ACEA ratings only refer to an oil's quality. For grade, you need to look at the SAE (Society of Automotive Engineers) ratings. These describe the oil's function and viscosity standard. Viscosity means the substance and clinging properties of the lubricant. When cold, oil can become like treacle so it is important that any lube is kept as thin as possible. It's cold performance is denoted by the letter 'W', meaning 'winter'. At the other end of the scale, a scorching hot oil can be as thin as water and about as useful too. So it needs to be as thick as possible when warm. Thin when cold but thick when warm? That's where MultiGrade oil comes in. For ages, good old 20W/50 was the oil to have. But as engines progressed and tolerances decreased, a lighter, thinner oil was required, especially when cold. Thus 15W/50, 15W/40 and even 15W/30 oils are now commonplace. Synthetics can go down as far as 5W which seemed unbeatable until Castrol came up with SLX - a 0W30 formulation! 'Free flowing' just doesn't describe it! It's predominantly a workshop oil retailing at around £10 ($15) a litre, but recommended for use in places like Canada in the winter. The latest offering to this 0W30 engineering miracle comes from AMSOIL.

So again: what should I buy? That all depends on your car, your pocket and how you intend to drive and service the car. All brands claim theirs offers the best protection available - until they launch a superior alternative. It's like washing powders - whiter than white until new Super-Nukem-Dazzo comes out. For most motorists and most cars, a quality mainline oil is the best. Ones which are known to be good at their job. Stuff like Castrol GTX. They're not too dear either. Don't believe the sales hype - they all perform to the same standards once they're out of the can and into your engine. Moving up a step, you could look at Duckhams QXR and Castrol Protection Plus and GTX3 Lightec. The latter two of these are designed specifically for engines with catalytic converters. They're also a good choice for GTi's and turbo'd engines. Go up a step again and you're looking at synthetic oils aimed squarely at the performance market. To get more money out of you, the manufacturers sell this stuff in smaller amounts which makes an oil change more expensive.

Marine Diesels and other special considerations.
Inland Marine Diesels (and certain road vehicles under special conditions) can, and do, glaze their bores due the low cylinder wall temperature causing the oil (and more importantly the additive pack) to undergo a chemical change to a varnish-like substance. The low temperature is caused by operating under light load for long periods.
This is related to engine design, some engines being nearly immune to it and others susceptible. The old Sherpa van diesel engines were notorious for this problem. The "cure" such as it is, is to use a low API specification oil, such as CC. Certain engine manufacturers/marinisers are now marketing the API CC oil for this purpose under their own name (and at a premium). You'll find some modern engines where its' industrial/vehicle manual states API CF and the marinised manual states API CC/CD. {Thanks to Tony Brooks for this information.}

Marine Oils.
I sometimes get asked "why are marine engine oils so expensive and why can't I just use regular motor oil in my marine engine instead?". Well, the National Marine Manufacturers Association Oil Certification Committee (click here for more info) introduced a four-stroke engine oil test and standard called the 4T certification. This specification is meant to assist boaters and manufacturers in identifying four-stroke cycle engine oils that have been specially formulated to withstand the rigors of marine engine operation. The certification was prompted by the growing influence of four-stroke engines in the marine market and their unique lubrication demands. So the simple answer is that regular road-based engine oil products don't contain rust inhibitors and won't pass the 4T certification. Lakes, waterways and the sea is a lot more aggressive an environment for an engine to operate around than on land.
Note : the NMMA have long had a similar specification for 2-stroke oils destined for marine use, called the TC-W3® certification.

The eBay problem
This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at The Car Maintenance Bibles, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to The Car Maintenance Bibles to see the full site and find my contact details. And now, back to the meat of the subject....

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Engine Oil Shelf Life.
I couldn't decide whether to put this in the FAQ or the main page, so it's in both, because I get asked this question a lot. Typically, the question is along the lines of "GenericAutoSuperStore are having a sale on WickedlySlippy Brand synthetic oil. If I buy it now, how long can I keep if before I use it?"
In general, liquid lubricants (ie. oils, not greases) will remain intact for a number of years. The main factor affecting the life of the oil is the storage condition for the products. Exposure to extreme temperature changes, and moisture will reduce the shelf life of the lubricants. ie. don't leave in the sun with the lid off. Best to keep them sealed and unopened.

Technically, engine oils have shelf lives of four to five years. However, as years pass, unused engine oils can become obsolete and fail to meet the technical requirements of current engines. The specs get updated regularly based on new scientific testing procedures and engine requirements. But this is only really a concern if you've bought a brand new car but have engine oil you bought for the previous car. An oil that is a number of years old might not be formulated to meet the requirements set for your newer engine.

If your unopened containers of engine oil are more than three years old, read the labels to make sure they meet the latest industry standards. If they do meet the current standards, you might want to take the extra precaution of obtaining oil analysis before using them. An oil analysis will check for key properties of the oil and ensure that it still meets the original manufacturing specs. Of course the cost of getting an analysis done on old oil is probably going to outweigh going and buying fresh stuff. So it's a double-edged sword.
As a general rule, the simpler the oil formulation, the longer the shelf life. The following is a guideline under protected conditions:

Product Shelf Life
Base Oils, Process Oils 3 years
Hydraulic Oils, Compressor Oils, General Purpose Lubricating Oils 2 years
Engine Oils and Transmission Oils 3 years
Industrial and Automotive Gear Oils 2 years
Metal Working and Cutting Oils 1 year

The following are signs of storage instability in a lubricant:

Settling out of the additives as a gel or sticky liquid
Floc or haze
Precipitates/solid material
Colour change or haziness
Water contamination in a lubricant can be detected by a "milky" appearance of the product.

"High mileage" oils.
More and more oil companies are coming out with "high mileage" oils now, some recommended for engines with as few as 75,000 miles on them. So what is a "high mileage" oil you ask? Well very generally speaking, these oils have two additives in them which are more suited to older engines. The first is normally a burnoff-inhibitor which helps prevent the oil from burning off if it gets past an engine seal into the combustion chamber. The second is a "seal conditioner", the exact makeup of which I'm not sure of, but it's designed to soak into seals such as head- and rocker-cover gaskets and force them to expand. Thus if one of the seals is a bit leaky, the seal conditioner will attempt to minimise the leak.
I've not had experience of high mileage oils myself, but a few people who've e-mailed me have passed on various tales from it being the miracle cure to it making no difference at all. I think the general rule-of-thumb though should be "if it 'aint broke, don't fix it." Just because your engine has over 75,000 miles on it, doesn't automatically mean you need high mileage oil. Is the exhaust sooty or smokey? Are you noticing oil leaks? Is the engine consuming oil? If your engine is working fine, the exhaust is clean and you're not noticing any problems, my guess is that it doesn't need high-mileage oil.

What about own-brands?
If you can't afford the big-name players, you could look at own-brand oils. These are usually badged oils from one of the larger companies but sold without the name, they are cheaper. Check the standards and grade ratings on the pack first! The example on the right is a local store in Chelmsford in England who sell their own label oil which is bottled for them by a volume retailer. The label tells you all you need to know.

Viscosity and Viscosity Index (VI).
The proper viscosity is the single most important criteria of a lubricating oil. The basic performance of machinery is based on the viscosity of the lubricant. Viscosity is, if you like, the resistance to the flowability of the oil. The thicker an oil, the higher its viscosity. The chart on the right shows a rough guide to ambient temperatures vs oil viscosity performance in both multigrade (top half) and single grade (lower half) oils.
Multigrade oils work by having a polymer added to a light base oil which prevents the oil from thinning too much as it warms up. At low temperatures, the polymers are coiled up and allow the oil to flow as it's low number (W number) indicates. As the oil heats up, the polymers unwind into long chains which prevent the oil from thinning as much as it normally would. The result is that at 100°C, the oil has thinned only as much as it's higher rating. Think of it like this: a 10W30 oil is a 10-weight oil that will not thin more than a 30-weight oil when it gets hot.
The viscosity index of a lubricant is an empirical formula that allows the change in viscosity in the presence of heat to be calculated. This tells the user how much the oil will thin when it is subjected to heat. The higher the viscosity index, the less an oil will thin at a specified temperature. Multi-viscosity motor oils will have a viscosity index well over 100, while single viscosity motor oils and most industrial oils will have a VI of about 100 or less.

Viscosity and oil weight numbers is quite a nauseatingly detailed topic. So if you're curious about why a 15W50 oil is so-called, then put on the geek shield and pop over to the Viscosity Page.....

Servicing and checking
For God's sake don't skimp on either of these. You can never check your engine oil too often. Use the dipstick - that's what it's there for - and don't run below the 'min' mark. Below that, there isn't enough oil for the pump to be able to supply the top of the engine whilst keeping a reserve in the sump. All oils, no matter what their type, are made of long-chained molecules which get sheared into shorter chains in a running engine. This in turn means that the oil begins to lose it's viscosity over time, and it uses up the additives in it that prevent scuffing between cams and followers, rings and cylinder walls etc etc. When this happens, fresh oil is the key. And don't worry about the engine oil turning black. It will lose it's golden-brown colour within a few hundred miles of being put in to the engine. That doesn't mean it's not working. Quite the contrary - it means it is working well. It changes colour as it traps oxidised oil, clots and the flakes of metal that pop off heavily loaded engine parts. Just don't leave it too long between oil changes.

So how often should I change my oil?

You can never change your engine oil too frequently. The more you do it, the longer the engine will last. The whole debate about exactly when you change your oil is somewhat of a grey area. Manufacturers tell you every 10,000 miles or so. Your mate with a classic car tells you every 3,000 miles. Ole' Bob with the bad breath who drives a truck tells you he's never once changed the oil in his car. Fact is, large quantities of water are produced by the normal combustion process and, depending on engine wear, some of it gets into the crank case. If you have a good crank case breathing system it gets removed from there PDQ, but even so, in cold weather a lot of condensation will take place. This is bad enough in itself, since water is not noted for its lubrication qualities in an engine, but even worse, that water dissolves any nitrates formed during the combustion process. If my memory of chemistry serves me right, that leaves you with a mixture of Nitric (HNO3) and Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary.
The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance travelled is probably one of the least important in most cases. Here is my selection in rough order of importance:

Number of cold starts (more condensation in a cold engine)
Ambient temperature (how long before warm enough to stop serious condensation)
Effectiveness of crank case scavenging (more of that anon)
State of wear of the engine (piston blow-by multiplies the problem)
Accuracy of carburation during warm-up period (extra gook produced)
Distance travelled (well, lets get that one out of the way)
If you were clever (or anal) enough, you could probably come up with a really clever formula incorporating all those factors. However, I would give 1, 2, and 3 equal top weighting. Items 1 to 3 have to be taken together since a given number of "cold" starts in the Dakar in summer is not the same as an equal number conducted in Fargo in January. The effect in either case will be modified by how much gas gets past the pistons. What we are really after is the severity and duration of the initial condensation period. All other things being equal, that will give you how much condensate will be produced and I would suggest that more than anything else determines when the oil should be dumped.

Dammit Chris, get to the point already!
Hang on a tic - if you really want the answer, there's a couple more factors you need to take account of: Crank-case scavenging (that's the clever term for sucking the nasty fumes back out of the crank-case) - or lack of it - is a crucial multiplying factor affecting all the other items listed above. As an example, the worst I've heard of was a Ford Fiesta of the mid 70s or so. It's crank-case fume extraction was via a tiny orifice directly into the inlet manifold which obviously could not handle any significant volume of crank-case fumes without upsetting the carburation. The car in question had been used almost exclusively for 5 mile journeys to/from work, shopping etc, and it had always been serviced "by the book". Despite (or because of) this, the engine was totally buggered at 40,000 miles. Alternatively you might get a car that by virtue of excellent crank case fume scavenging could tolerate many more cold starts than one without.

Taking all these into consideration, my philosophy would be to totally ignore the distance and change the oil three times a year - about November, February and May. Move these dates a bit according to the severity of the winter. An average family car will do around 14,000 miles per year and about 2/3 of that will fall in the May - November period. At the end of that period, the car will have just about touched on the recommended oil change distance - but all done at reasonable temperatures and including long distance runs during vacations and good weather. During the Nov - Feb. period it may accumulate only 2 or 3 thousand miles, all low temperature starts and mostly short runs. The Feb. to May period is likely to be about the same.
About 10 or 15 years ago, an article in the ANWB journal (ANWB is the Dutch equivalent of the AA - or the AAA in the American case) reached more or less the same conclusion that distance was not very important. In their case they applied this to their road service fleet, which typically once started in the morning never got cold. In effect, they hardly ever changed the oil! I seem to remember 30,000 miles between oil changes being quoted. I also seem to remember that they had some kind of water or acid indicator attached to the end of the dipstick and went by that rather than distance.

That's a politician's answer - you've dodged the entire issue!

Have I? I don't know how far you drive in a year, where you live, the style of your driving or anything else so I can't tell you what's right for your car. Personally, I changed the oil and filter in my 1985 Audi Coupe every 5,000 miles. It had done over 150,000 miles when I sold it, wasn't leaking and didn't consume any oil. If you must have a figure from me, then 5,000 is it.

What else happens when I change the oil then?
Engines pump about 10,000 litres of air for every litre of fuel consumed, and along with all that air, they suck in plenty of dirt and grit. A good air filter will stop everything bigger than a micron in diameter - everything smaller mostly just floats around harmlessly in the 0.001inch minimum thickness oil films that separate all the moving parts. Despite all of this, there will always be submicron particles that get in and there will be places in the engines oilways where they will gather. Every time you empty the oil from your sump, you're also draining this fine grit with it.

Checking the oil in your engine, and topping up.
Note that this section only applies to wet sump engines - the type found in most consumer vehicles. For more info on sump types, see Wet sumps vs. dry sumps below.
To a lot of people, this little section could be categorised by the rearranging the words "granny eggs teaching suck your to". But you'd be surprised by the number of people that don't know how to do even this basic task. When checking the level of oil in the engine, the car should be on a level plane, and should be relatively cold. I've run into several people lately who insist in keeping the crankcase topped off completely, and they invariably check the dipstick just after shutting down the engine. Reading the oil in this way results in an erroneous reading because a quantity of oil (usually about half a litre) is still confined in the oilways and passages (galleries) of the engine, and takes some time to drain back into the crankcase. (On the image, the blue areas are where oil is likely to still be running back down to the sump). On seeing what appears to be an abnormally low level on the dipstick, these people then add more oil to the oil filler at the top of the engine. The oilways and passages all empty, and suddenly the engine becomes over-filled with oil, going way above the 'MAX' mark on the dipstick.

What happens when an engine is overfilled with oil?
So you topped up the engine when it was warm after getting a faulty dipstick reading, or you put too much oil in when you changed it yourself. What's the worst that could happen? Well the problem with this is that the next time the engine is run, the windage in the crankcase and other pressures generated by the oil pump, etc. place a great strain on the seal on the rear main bearing.
Eventually, often much sooner than the ordinary man in the street might expect, the rear main bearing seal ruptures, and the engine becomes a 'leaker'. If you've got a manual gearbox, this means one thing: this oil goes right onto the flywheel and the face of the clutch disc. A lubricated clutch is A Bad Thing. If this still goes unnoticed, the front seal is the next to go, and the engine then becomes a 'gusher' (or to be more colourful, it starts pissing oil all over the place). As well as smothering the clutch with oil from the rear, the oil now coming from the front leak will be neatly distributed about the engine bay as it hits the front pulley - often propelling it out as far as the brake discs. At the same time as this Hollywood disaster movie is unfolding outside the engine, things aren't working out any better on the inside. As you can see from the diagram, the correct oil level is really close to the rotating crank. Overfilling will mean the crank dips into the oil and churns it into a froth. Froth is good on certain types of coffee but not good in an engine. The mixture of aerated oil will be forced into the bearings and in case you didn't know, air is not a lubricant. Typically this means that bearing damage will follow quite rapidly, especially if you are driving on a motorway. You'll know bearing damage when you get it. The engine smells like a garage mechanic cooking over an open flame and the noise coming from the engine is the sort of thing you'd normally hear in vaudeville plays when a piano is pushed down a flight of stairs. As if that all wasn't bad enough, the excess oil gets thrown up into the piston bores where the piston rings have a hard time coping with the excess oil and pressure. It gets into the combustion chamber and some of it will get out into the exhaust system unburned resulting in a nice patina of oil all over the platinum surfaces of your catalytic converter. This renders it utterly useless for good.
Well, you did ask.

So what's the best way to check the oil level?
If your engine is cold (for example it has been parked overnight) you can check the oil level right away. The oil will have had time to settle back into the sump. Just make sure the car is level before you do. If the engine is warm or hot (after you've been driving) then you should wait for 30 minutes or so to let as much oil as possible drain back into the sump. Checking it first thing the next morning is ideal.
It's worth pointing out that you should double-check your owner's manual too - some cars, like I the '92 Porcshe Carrera, require that the oil is checked while the engine is running and the oil is at temperature.

Like the site? Help Chris buy a bike. The page you're reading is free, but if you like what you see and feel you've learned something, throw me a $5 bone as a token of your appreciation. Help me buy the object of my desire.

Wet sumps vs. dry sumps.
Almost all passenger cars, trucks and SUVs use what's called a wet sump system. If you look at the diagram above you can see the sump (or oil pan) is the lowest part of the engine. In a wet sump system, excess oil drains back into the sump when it has passed through the engine, and the oil pump then sucks it out of the sump and pumps it back to the top of the engine. The advantage of a wet sump is that it's cost effective to build and maintain and it makes oil-checking easy for the average driver. The disadvantage is that cornering and braking can cause the oil to slosh around in the sump. This can cause the oil to not cover the oil pump pickup tube, which could starve the top end of oil, or it could get deep enough in a severe cornering maneuver to bog-down the crank, which is A Bad Thing. To counter these problems, a lot of wet sumps now have baffles in them to stop the oil moving around so much, and for your average road-going consumer-level vehicle, this is a fine compromise.

Dry sumps
When it comes to racing vehicles, wet sumps simply have too many disadvantages. Instead, race engines typically use a dry sump. As its name implies, the sump of the engine is dry - it never fills with oil. In a wet-sump system, the sump has to be large enough to accommodate all the oil from the engine when it is turned off. In a dry sump system, that requirement is gone so the sump can be much much smaller. (In the image on the right, the right-most sump is representative of a dry sump). A smaller sump means the engine can be mounted lower down in the vehicle, which in turn lowers the centre of gravity. So how can this be? Well a dry sump system uses a remote oil reservoir or tank, and a either a second oil pump, or a single multi-stage pump. In a double pump system, one oil pump works just like a wet sump - it distributes oil to the top end of the engine, but it pulls the oil from the reservoir instead of the sump. The second pump scavenges the oil from the sump and returns it to the reservoir. In a single pump system, one pump is either a three- or four-stage pump. It has multiple circuits running off the same pump to pressurise the engine and scavenge oil back from the sump. The advantages of dry sumps for racing become obvious when you examine the design. The engine can be mounted lower in the chassis because of the shallow oil pan. The pumps typically don't run off the crank-driven belts so no engine power is sapped in driving them. The remote tank or reservoir can be pretty much any size you like and be mounted anywhere in the vehicle (usually low down again for centre of gravity reasons). There isn't oil sloshing around in the sump so you don't run the risk of bogging down the crank. For all these reasons, dry sumps are considered to be safer and far more dependable than their wet counterparts. So if it's that much better, why don't you find this system in consumer vehicles? Simple. The increased weight, complexity and cost of having larger or more pumps and a remote reservoir with all the additional high pressure oil lines involved. For a racing team, this isn't an issue, but for Toyota or Ford, adding that sort of cost and complexity to their passenger vehicles is just a no-go.

Can I use car engine oil in my motorbike then?
No you can't. Or at least I wouldn't recommend it....
The real answer to this question lies in the type of motorbike you own. If you own a bike with a wet clutch (ie. where the clutch sits partially submerged in the sump oil) and you dump car oil into it, all sorts of nasty things happen. Oils formulated for car engines have friction modifiers in them. When the engine oil gets into the clutch, the friction modifiers get to work and you'll end up with a clutch that won't bite. In addition, the chemical makeup of some car oils has been known to soften the clutch material on motorbikes to the point where the entire clutch pack fails. Bike oils generally don't have friction modifiers, so they don't have this problem. If you're not sure, check for a JASO MA spec on the bottle. If you see that on the label, then it means the oil has been tested and confirmed to work with a wet clutch. Mobil have cautionary information on exactly this subject on their Motorcycle Oils FAQ page.
The other side of this coin is if you have a dry clutch bike, like some BMWs. In this case, the clutch is configured similar to a car in that it's never in contact with the engine oil, and if that's the case, then regular car engine oil might provide all the protection and lubrication you need for your bike. The issue then becomes a question of the exact formulation of the oil. The additive packages for car engine oil are typically balanced differently than those for motorbikes with fuel economy and emission system protection being the higher priorities. Your typical passenger car doesn't rev to 12,000 rpm either so stuffing normal car engine oil in a motorbike engine that can run to double or even triple the rpm of a car engine could cause all sorts of problems.
The debate about whether any of this is true is burning in many forums across the internet. One site in particular casts some doubt on the issue, claiming the only difference between car and bike oil is the price. I don't subscribe to that theory but in order for you to make your own decision, here's a link: Testing motorcycle oil.

Can I use diesel engine oil in my petrol engine?
Not really. Diesel engines run much higher compression ratios than petrol engines and they run a lot hotter, so the oil is formulated to deal with this. Plus they produce a lot more dirt in terms of combustion by-products. Diesel-rated oils typically have more detergents in them to deal with this (see Using Diesel oil for flushing above). It's not unheard of for diesel oils to clean a petrol engine so well that it loses compression. Diesel-rated oils also have an anti-foaming agent in them which is unique to diesel engines, and not needed in petrol engines.

And so to engine additives
Think what you will of these. Whatever you call them, they are an addition to the engine which it was not designed to take. Engines are designed to use engine oil, not Teflon®. Make up your own mind - read this report and see what you think. In my opinion (and that doesn't mean I'm right) the majority of these are primarily a placebo to put uneducated minds at rest whilst making a nice profit for the additive manufacturer.
The additive part of this site started quite small, but as more and more of the companies got into lawsuits and legal actions, and lost, this page became far too long to read all in one go. So if you're considering Duralube, ProLong, Slick50 or any of the other brand-name placebos, you'll be wanting to hot-step it over to my additives page pretty darned quickly.....

Not something off Star Trek, although it sounds like it. Nanolubricants use the geometrical properties of miniature particles to provide lubrication. A couple of companies are working on these new generation lubricants; New York-based Applied Nanomaterials (ApNano) is one of them. Their R&D lab in the commercial arm of the Weizmann Institute of Science in Israel is initially developing an onion-type nanostructure, i.e. a multilayered hollow structure of nested spheres called NanoLubTM. According to the theory of the company's founders, such a structure can replace lubricants, because it works like a box moving along a near infinite layer of super-miniaturized ball bearings. They claim that respected institutes worldwide have proved that powder made from these nanostructures is six to ten times more effective than regular lubricants.
In their case, the nanospheres are built from tungsten disulfide (WS2). The layers slide past each other, reducing friction, while the hollow cores provide flexibility. Applied Nanomaterials claims the materials can withstand immense pressures. The material acts as a kind of solid ball bearing between the metal layers, rather like the wheels of a tank tread. In addition, the nanostructures insert themselves within each metal layer, while other nanostructures slide over them, creating a smooth layer at the molecular level.

The idea is that unlike oil, the nanolubricant never wears down; it is permanent and requires no maintenance. Theoretically, a nanolubricant can be used for various friction reducing applications, such as on the outer coating of ships and planes to reduce water and air friction, respectively. If you're that way inclined, think of what it could do to the sex toy industry....

The powder will eventually stand on its own as a lubricant, however Applied Nanomaterials realizes that recognition of the technology requires collaboration with lubricant manufacturers as an additive to existing lubricants. The problem of course is that if this lubricant never needs changing, anyone who decides to mass manufacture and market it is going to lose a chunk of revenue - once you dump it in your engine, you never buy any more. Great for you and me, bad business model for the company who dares to market it.

Applied Nanomaterials competitors are developing similar materials, but based on nested carbon nanotube structures that over time tend to disintegrate under friction from the materials they lubricate.

Don't expect to see NanoLubTM on the shelves in large quantities just yet though. It can take a day to manufacture just 750g of the stuff. At the time of writing, it was being marketed by SONOL Israel Fuel Company

An alternative to engine additives: pre-pressurisation
What the additive manufacturers tell you is true - when you start your engine, there really is very little oil in the right place - most of it is in the sump. There is another alternative. I found a site called and they seem to be offering an interesting alternative. They have a system which uses a cylinder of pressurised oil and a solenoid valve, all connected to the regular oil system. It works with only one moving part, (the solenoid valve - duh!). When the key is turned on it opens the valve and the oil that was trapped in the tank the previous time it was running goes back into the oil gallery in 1 or 2 seconds and the low oil pressure light will flash off. There's likely to still be a little lag before full-on lubrication gets to the main bearings, but from what I can tell, this system will massively reduce that lag compared to starting from cold - it pressurises the system before the starter engages. Of course an engine that has set up for a few months and is completely dry will take a few more seconds. When the engine is turned off the solenoid valve shuts off in 30 milliseconds so you end up with pressure on the tank equal to the pressure the last time it was running. The tank will hold more than enough oil to accomplish this. Its completely over engineered as the tank is rated for over a thousand pounds and the hose is good for 300lb. Because the valve is designed for an industrial application with an expected duty life of several million cycles, AutoEngineLube give it a lifetime warranty. It only uses previously filtered oil from the gallery so no damage can be done by it in any way.
Their system comes as a kit and requires some menial installation - most savvy home mechanics should be able to do it. I'm not sure how it would affect the warranty on a car engine. In theory, if it works, it ought to make no difference but you know what manufacturers are like - if you even sneeze on your engine, it's likely to void the warranty.
Pop over and check them out if you're interested. If you end up buying one of these, I'd like to know what sort of results you get so I can add an objective review to my site. can be found here. Another site sells a similar product - can be found here.

It's worth pointing out that pre-lubers have been around for quite a while; the original systems featured an electric pump that circulated the oil from the sump before the starter turned. The pump would bring the oil up to full operating pressure before you attempted to start the engine. A reader of this site e-mailed me about this. He had one on an old MG-TD, because the car got very infrequent use; it worked rather well and he never had any major engine problems with it installed. still do the "old style" pre-lubers but their website has vanished so I don't have a good link for them now.

Case study: MOROSO Accumulater (pistonless upright bottle type) pre-oiler on V8 Zephyrs

A reader contacted me about using pre-oilers on classic vehicles. Here's what he had to say:
"I use the MOROSO Accumulater 2 which is a pistonless upright bottle type. I researched these after experiencing oil pressure drops of 20psi on uphill right hand corners at speed. The Moroso 2 cured it right away. I plumbed it directly into where the oil sender went and used a tee for the oil light sender. I have a ½" ball valve at the bottle I use but intend to rig a choke cable to use it from inside the car. Electric solenoid valves are available too. To do an oil change the factory fitted tire valve is pumped with 20psi of air and the tap opened, old oil is then fully pushed out into the sump via the oil feeds.
The car if used for racing etc is driven with the ball valve open, any drop in oil pressure is taken over by the accumulater until the oil pump pick up is covered again. I also use the oiler to lube the engine (Ford V8) by turning the valve with the engine off, the oil pressure goes up to about 20-30psi (you can hear it gurgle in the rocker covers!). After 10-15 seconds I then start the engine. You turn the valve off with the engine running to trap oil for the next start up.Racers run these on engines that can be "claimed" after a race as if the engine had a high doller sump pan they would lose it with the engine. The Accumulater works better than any trap door or baffled sump if you spin backwards off a track too!"
There are further writeups of this particular installation available at the MKIII Zephyr V8 site and at

Oil filters and filtration.
Thanks to one reader who noted that in all of this page, until mid-2001 I had not given much, if any space, to the topic of filters and filtration. So here we go.

It's all very well changing your oil often, but it's not just the oil that helps prevent engine wear. The oil filter does its part too. Dirt is the prime cause of engine wear. Not big dirt, like you'd see in a yard, but minute particles of dirt. It's dirt nevertheless, and it's abrasive. These contaminants vary from road dust (which are razor-like flakes from an engine's perspective) that doesn't get filtered out by the air filter, up to actual metal particles - the byproducts of the casting scarf from the original engine manufacture, and basic engine wear. All this nastiness is carried around by the oil into the minute parts of your engine, being rammed into the precision clearances between bearings and other moving parts. Once in, they don't come out easy, but tend to stay there, wearing grooves, grinding and generally messing up your engine. Other debris that causes problems are a by-product of the mere way an engine works - sooty particles from the combustion process can be forced past the piston rings and transported around in the oil too. This is definitely A Bad Thing - the soot acts like a sponge and soaks up other oil additives reducing the oil's anti-wear properties, and messing up it's viscosity. All this dirt is why oil goes black when it's used. That lovely syrup-like yellow that it is when you put it in is pure oil. The black stuff that comes out at an oil change is the same oil full of contaminants and by-products from wear and tear.

That's where the oil filter comes in. It's job is to catch all this crap floating around in the oil, and to stop it from recirculating. Most oil filters that you or I will ever see are the spin-on type. They're shaped like an aluminium can and spin on to a threaded oil feeder poking out of the side of the engine somewhere. They're called 'full-flow' oil filters because they sit in the normal flow of the oil through the engine. Sort of like an electrical component in series with all the other electrical component. Because it sits in-line, it has to be designed not to restrict the flow of oil around the circuit, and thus can only really be effective at stopping the larger particles. Large, in this case, is around the 20micron size. So here's the catch. The smallest contaminants are in the 10-20micron size range. Not only is that "extremely small", but it means that they pass right through the oil filter and back out into circulation. This is why regular oil changes are a necessity, because these tiny little things can be the most damaging.

This is an exploded view of a typical spin-on oil filter used in automotive applications. I've sliced the filter element (the brownish-yellow part) so you can see the internal structure of the filter). Typically the engine oil enters through the ring of 5 or 6 holes in the base and into the main cannister. From there it is forced inwards through the filter element, through the drain holes in the central core and out through the central, threaded hole in the base.

There is another alternative, but it's only really used in heavy applications or for racing. That alternative is to fit a secondary bypass oil filter. This is sort of like a filter in parallel with the primary one. It doesn't restrict the flow of oil in the main circuit, but the oil that passes through it is filtered down to the 5 micron range, thus removing even the smallest contaminants. The newest filters claim to work down to 1 micron, though I can't confirm nor deny those claims. The upside is that by cleaning the oil so completely, bypass oil filters increase not only engine life, but also the life of the oil itself. This means longer service intervals.

Magnetised oil traps
Recently, magnetic filter additions have started to surface. I was sent one in 2001 to try out and it really did seem to work. The product in question was called the Bear Trap BT500. Their website can be found here (now owned by One Eye Industries). It's basically a sleeve made of foam rubber and plastic with some magnets in it. It bends to clamp around the outside of your regular spin-on oil filter. The idea is that the magnets will attract any metal debris in your oil and stick them to the inside of the oil filter wall, thus preventing them from going back into the oil circulation. Being of a curious nature (or stupid, depending on how you look at it) I decided to dismantle my oil filter after using the Bear Trap for 5000 miles. I learned a couple of things.

You shouldn't try to do this yourself.
It's bloody messy.
But most importantly, after a brief period in accident and emergency to stitch up the gash in my hand, I discovered that sure enough, there were tiny arrangements of metal filings clustered around the inside of the oil filter wall where the magnets from the beartrap had been. You'll excuse the lack of photos to prove the point, but I had other things to worry about. If you visit their website or that of FilterMag (below) you'll see similar cutaway photos.
So can I recommend their product? Yes.

Another alternative to the Bear Trap is the FilterMag - essentially the same style of product but from a different manufacturer. FilterMag can be found at this link.

An alternative to custom magnetised oil traps.
Thanks to John Nightingale who read my pages and then felt he should contribute something. For those of you who do more than just change your filter - ie. take off the oil pan completely, John writes:
" Next time you are in the mall or high street, drop into the Radio Shack or a hardware store and purchase a package of modern, powerful ceramic magnets. These are available in various shapes and they are cheap. Radio Shack sells a package of two wafer shaped magnets, for instance. Stroll out to your car at the end of your shopping trip, bend down and stick these magnets onto convenient flat surfaces the bottom of your oil pan either side of the drain hole or as convenient. Now the magnets will magnetize the steel of the oil pan in their area. On the inside, particles coming through the field established by a magnet will be sequestered by being stuck to the bottom of the oil pan. Next time you take off the oil pan, clean it out in the usual way, pull off the magnets from the outside, clean them up and then stick them onto the inside of the oil pan at the bottom but clear of the drain hole. This will give an even better result since now the oil is exposed to the naked magnets themselves. The bottom of the oil pan in the area of each of the magnets is also magnetized, of course, and contributing to the effect. Resist the temptation to stand the magnets on edge to expose more of their surface to the oil. Placing the magnets flat on the oil pan uses the oil pan's steel as a keeper for the magnets and will ensure that they stay powerful. Placing the magnets flat will increase the area of the oil pan that is part of the magnetic circuit so you will loose no particle pick up area by having the magnets lying flat. "

Magnetised oil traps - doing it yourself.
There's nothing really special about magnetised oil traps other than the type of magnet they use. Bear Trap and FilterMag basically offer a consumer-oriented product. But if you're a tinkerer, there's nothing to stop you doing it yourself. The magnets normally used are Neodymium, nearly the most powerful nonelectric magnet type. They are the kind of magnet used in computer hard drives, often coming in pairs held just a few millimeters apart with the back end of the hard drive head assembly (the part being made of coiled wire) in between. If you can find a couple of old hard drives - try the local computer junk store - you ought to be able to disassemble them and take the magnets out to stick to your own oil filter. John Nicholas Sarris, a reader of my site, suggested this and provided the following photos as an example.

An open hard drive. The magnets (one visible) are in the upper left corner and are crescent shaped.
The top magnet plate has been removed. As you can see on the lower magnet it is attached to a metal plate. I presume this it to keep the magnetic field from the magnets between the two magnets and not extend outside the hard drive case.
The hard drive's head assembly has been removed. The lower magnet attached to its plate is clearly visible.
A pair of hard drive magnets side-by-side. They are still attached to their metal plates because the adhesive used to attach them is immensely strong. I once removed a hard drive magnet from its plate, but broke it in half in the process.
The same magnets holding themselves to my hand. I could have them stick to each other through my palm, but it was hard to take a good picture. This actually hurt my fingers a bit. As you can see they are strong despite being only 2mm thick. The plate they are attached to itself is 3mm thick.

The importance of neodynium magnets
I thought it worth pointing out here what a potential disaster awaits the home tinkerer if you just grab any old magnet and stick it on the outside of your oil filter. Your common or garden ferrous magnet, like those horrible souvenir magnets stuck to your fridge (you know you've got some) are usually made from iron, and thus have a limited life span which in some cases can be as short as 6 or 12 months. During this time they progressively lose thier power. Not enough for that hideous magnetic photo frame to drop off the fridge, but enough to be a problem if it was stuck to your oil filter. Why's that then? Well, come the end of the filters life, just as the magnet is weakening and the collection of metal particles is at it's highest, one good jolt and it could dislodge, and a large collection of metal shavings and filings could detach from the inside of the filter and find its way back into your engine all in one go. That would be bad. So as much as you might like the magnetic photo of granny and the giraffe from Whipsnade zoo to be stuck in a filthy oily place on your car, don't do it.

Larger filters on standard cars?
There's a school of thought which says that enlarging the oil filter on your car is A Good Thing. Why is this?
The small oil filters fitted to engines these days run with quite a high back pressure, and the bypass valve trips at about 3500rpm. That means that your oil is not being filtered when the engine is spinning faster than 3500rpm. As the oil filter does its job and starts to clog up, that rpm value can be lower.
If you increase the size of the filter, this will raise the rpm at which the bypass valve will switch. With a bigger filter and lower back pressure, for the same rpm (prior to bypass valve operation) less engine power will be lost in the filter. Bigger filter means better filtering and more power at low to mid revs. Clever eh? But there's some things you need to be aware of if you're going to try this approach, all of which are relevant, and none of which I can confirm or deny

Bigger filter = more "dead" space = more oil. Remember you'd need to add more oil to the engine to keep the oil level at the correct mark on the dipstick. This isn't necessarily a bad thing - more oil doing the same job theoretically means less stress on the oil.
Oil may take a little longer to circulate around the engine after startup, as the pump may have to fill up the larger capacity oil filter. With modern filters this ought not to be a problem though because all but the cheapest filters have backflow preventers which keep oil in the filter when the engine is off.
Availability of filters and fouling. If you put a larger filter on it might foul something else in the engine bay. That is if you can find a larger filter to start with. The rule of thumb is to go to a motor factors shop, and find the oil filter that was designed for your engine .Then look through the myriad of larger oil filter boxes for a bigger filter that has the same screw thread and sealing ring diameter. Nowadays most spin-on filters have a 20mm screw thread so that's not going to be the hard part. Finding the same sealing ring diameter is the thing to be careful of. And don't ask the people at the parts counter. Because of liability issues, they're unlikely to sell you anything other than exact filter for your make and model of vehicle.
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A Practical example of the proper procedures saving an engine.
I started these pages back in 1994 and have been adding to them ever since. I've always followed my own advice and in 2005, it paid off big time. I'll tell this in the past tense because it'll get lost in the page and I'll forget to update it when I change motorbikes.
So I owned a 2001 BMW R1150GS motorbike. I bought it pre-owned from my local dealer who assured me it had been through the workshops as part of the "standard procedure" of them taking a bike in and re-selling it. For 2 years I'd been riding it with horrible engine noise and engine detonation (pre-ignition). Every time I took it back to the dealer, they were adamant there was nothing wrong with the engine, and that "they all do that". Not believing them, I finally found an independent BMW specialist who took the engine apart for me. It turned out the BMW dealership had lied - the bike had never been in their service department. This was evidenced by the fact that the cylinders had sand in them. The dealership had never bothered to check the bike and wouldn't believe my complaints about the noisy engine. The independent mechanic fixed it all up for me - an $1100 repair bill that involved basically stripping down the entire engine, honing the cylinder barrels, putting in new piston rings, cleaning the pistons, barrels, heads, throttle and airbox, flushing and cleaning the whole thing and putting it all back together. The point is that during the two years I'd been riding it with sand in the engine, I'd been religiously topping up the oil and changing the filter. It's a testament to BMW engineering that the engine ran without seizing up, but it's also a testament to paying attention to your oil changes. If I'd let it slide, or not done the filter, that engine would not have been a rebuild - it would have been a far more costly brand new engine.

This is all great. Now how do I actually change my oil?
A good number of readers will get to this point in the page and think "this is easy - I could do this!", and for the most part, you can. Below is a generic, idiots-guide to changing the oil in your engine. It's not specific to any particular car but ought to cover most engines.

Before you start, you'll need the following :

new oil (duh!)
a drain pan
an oil funnel
a socket wrench set and / or hex wrench set (allen wrenches)
an oil filter remover
a new crush washer
nitrile gloves (not latex - mineral oil eats latex gloves)
engineer / shop manual, if one is available
Start your engine and run it for a couple of minutes to get some heat into the oil
Leave the engine to stand for 5 or 10 minutes. When you started it, it heated the oil but it also filled the oilways. You want the oil to drain back to the sump.
Take the dipstick out or loosen it off and break the seal where it plugs into the engine dipstick tube. This prevents a vacuum building up behind the oil when you start to drain it.
Get your drain pan / oil container and stuff it under the sump. Make sure it's sitting under the sump drain plug. I Really like the combined drainer / container types. They look like regular oil containers but if you lay them on their side, there's a pop-out plug. When you drain the oil, it runs into the side of the container, then you can put the plug back in and use the same container to take the oil away.

Put your rubber gloves on. Try to use the disposable type. Your mum / wife will never forgive you if you use the washing-up gloves. Remember - used oil is toxic and carcinogenic. If you get it on your skin, it could cause problems. Use your socket wrench or allen wrench to loosen the sump plug just slightly. Once it's loose, remove it by hand.

Be amazed as the black syrup runs out of the engine and into your container. Be more amazed how, if it's windy, those last dregs just won't hit the container no matter where you put it. They will however go all over the road/garage floor/cat.
Remove the old crush washer from the sump plug and throw it away. Replace it with a new one. Use some of the oil from the drain container on the end of a rag to wipe around the drain hole in the sump. This will help clean any mess away and leave you with a smooth surface. Screw the sump plug back in by hand until it's finger tight and then use your wrench to crush the washer. This can vary from a quarter turn to a half turn. Don't overdo it or you'll strip the threads. Similarly, don't leave it too loose or it will fall out. If in doubt, use a torque wrench set to the value indicated in your shop manual.

Now get your oil filter remover out. Push the oil drain container under the oil filter - when you spin it off, there will be a lot of oil comes out. Use the filter remover to grip the oil filter and spin it off anticlockwise. 99.9% of oil filters take some muscle to get going. This is why a filter remover is a must-have. Stabbing the filter with a screwdriver and using brute force may work, but you'll be finding oil all over yourself for weeks to come if you use that method. Apart from that, some cars have aluminium inserts that protrude out of the engine block into the body of the filter, so firing a screw driver into the filter near its base (the strongest part) may shear that aluminium bit off the engine block. That Would Be Bad. If you really can't lay hands on a filter wrench, try sandpaper - wrap it around the filter, sand-side-in and grip the paper backing - you might be able to spin the filter off like that.
Once the filter is finger-loose, spin it off by hand. (these things below are filter removers)

Clean off the face of the oil filter mount on the side of the engine block using a rag. Use a little oil on a rag to wipe around the seal of the new filter and spin it on by hand. Once it's locked against the side of the engine block, another quarter-turn by hand is normally enough to secure it in place.
Pull the drain container out from under the car and use a rag to wipe down any excess oil that has spilled down the side of the engine block. Pay attention around the sump plug and the filter. These are places you'll be checking later for leaks so the cleaner they are now, the better.
Use a little WD40 on the oil container and an old rag to clean the remaining oil down into the container. Put the plug back in and make sure it fits snug. That's your waste oil. Don't drink it.
Up to the top of the again engine now. Put the dipstick back in. Find the oil filler cap and take it off. It might say "OIL" or it might say "710". It is not a "710 cap" as one person once asked for. "710" is "OIL" upside-down. Some people need to be told....
Look in your shop manual for the system capacity with filter change. This will be more than the capacity without a filter change. A lot of oil containers now come with capacity marks on the side of them. Put your oil funnel into the oil filler hole and pour in the right amount of oil. Do it slowly. If you do it quick, you'll get airlocks and the funnel will burp oil in your face.
Once you're happy you've got enough oil in there (check it with the dipstick if you're not sure), remove the funnel, replace the oil cap and replace the dipstick.
Pull the main high tension wire from the distributor cap or in some way disable the engine so that you can crank it over but it WILL NOT start. (Note : you might want to pull out the fuel pump fuse too - if you crank the engine without it starting, it will still be pumping fuel - that could cause a backfire or damage the catalyst). Crank it over until the low pressure light goes off, and another 15-20 seconds for good measure. You are pumping new oil into the empty filter and then expelling all the air from the oil lines and cavities.
Replace the high tension lead (and fuel pump fuse) and start the engine and let it idle for a minute or so. Stop the engine. I don't want you crawling under a car to look for leaks when the engine is running. There's so many things that can go wrong with spinning fan blades, belts, human hair, clothes, fingers and the odd dodgy auto-gearbox that will slip into "D" and run you over.
With the engine off have a look at the side of the engine block around the oil filter. Check the area around the sump drain too. Both should be as clean as you left them with no sign of leaks. If there's a leak, a little tightening of the drain plug or filter should cure it.
One reader suggested and additional step before (9) above. When he changes his filter, he fills the new one up with clean oil and waits for it to soak into the filter itself. Once he's satisfied that the filter is soaked, he pours the excess oil out of the filter and then screws it on to the engine.

Job well done. Now you should have hands that smell of talcum powder and rubber (from the gloves), a couple of greasy, slippery tools and a container full of old oil. Oh, and a crush washer and filter. If you've got more than this, you took something off that I didn't tell you to. If you turned the engine off before checking for leaks, you should also have a full complement of fingers, hair (if you had it to start with) and you should still be fully clothed. Congratulations. You've changed your engine oil.

Using oil extractors

There's another way of getting the oil out of your car's engine during an oil change - oil extractors. The typical extractor uses a vacuum mechanism either generated by you pumping a handle to build up a vacuum in the reservoir, or by a powered vacuum pump. The example on the right is a manual style. Basically you pump the handle to build up a vacuum, then poke the extractor hose into the oil and let her rip.
Extractors are a convenience item designed to eliminate the need to get your vehicle up on a ramp, or for you to crawl under it and deal with the drain plug. The only problem with an extractor is that you can never be 100% guaranteed that you get all the oil out. For it to work best, the suction hose needs to be in the lowest point of the sump pan, where the drain bolt is. The problem is that first of all, the sump isn't transparent, so you can't tell where the suction hose really is. (Remember you'll be feeding it in through dipstick tube). Second, a lot of sumps have anti-slosh baffles in them both horizontally and vertically. If you don't get the extractor pipe through one of the baffle holes, you'll be leaving the entire sump's-worth of oil in there. Third, and finally, any congealed oil, clogs or clumps of sludge will likely get stuck in the extractor hose causing a blockage. That would mean taking the hose out, cleaning out the blockage, then feeding it back in again which subjects you to the initial two problems all over again.
Oil extractors are more commonly used for getting oil out of smaller engines like lawnmowers. I've never used one in a car engine but because of the problems mentioned above, I can't imagine it would be especially efficient. Having said that, the Smart car has no sump drain so the only way to get oil out of those things in a service is to use an extractor.

Finally, and just as importantly: Disposing of used engine oil.

Think about it for a minute. What did you do with that last oil change? Pour it away down a drain? Seal it and bin it? The annual average for oil which is just washed away is 720Million gallons! About 120Million of that is from tanker spills which leaves another 600Million from domestic and business disposal. This all ends up polluting the groundwater.
So what can you do? Well, you can dispose of your used oil properly. Firstly, it's worth noting that engine oils which have been used are mildly carcinogenic. This means cancer, specifically skin cancer. To be safe, wash any off quickly with a de-greaser like GUNK. For heavens sake, don't use petrol (gasoline) - most fuels contain long chain hydrocarbons, which when exposed to skin pass right through to the blood stream. (This can mean liver damage, and possibly failure) Better still, wear protective gloves. Once the oil is drained into a suitable container, try your local garage. All garage workshops must have disposal barrels and many will allow you to dump your oil into their barrels. In the UK, many DIY superstores now have oil disposal banks where you can empty your used oil, and it's collected every couple of days by a tanker. So next time, just think about first. If only for the fact that in most civilised countries, it's actually an arrestable offence to dispose of oil in the public sewerage system. If you live in the UK, phone 0800 663366 to find the location of your nearest oil bank. Alternatively, you can use the postcode search on the oilbank website.

Premium Member
3,084 Posts
Somewhat disappointed that my favorite and one of the best synthetics was not used! ( Royal Purple).

562 Posts
Wow, tons of great information. After reading the first article, I immediately thought of the engine block heaters on diesels. After a small amount of searching I came up with this to solve my cold start issues.
Moroso 23991 Moroso Self Contained Oil Preheater

Sorry if this is not a kosher post, But i honestly think this is a viable solution to the problem of cold starts and there is no mention of it upon searching.

Premium Member
8,831 Posts
Wow, tons of great information. After reading the first article, I immediately thought of the engine block heaters on diesels. After a small amount of searching I came up with this to solve my cold start issues.
Moroso 23991 Moroso Self Contained Oil Preheater

Sorry if this is not a kosher post, But i honestly think this is a viable solution to the problem of cold starts and there is no mention of it upon searching.
Or you could get a OEM one for half the price!!!



562 Posts
:agreed: Either way, after reading the article I'm convinced this should become a common practice. If i read correctly, Used a few hours before starts, this would theoretically decrease around 70% of engine wear? :dunno: Seems worth the time and 30 or so bucks...

It's too cold here
335 Posts
Since we're talking about oil, I've heard that once you put synthetic oil in your vehicle, you can never switch back to regular oil, even after an oil change. Not sure I believe that. What do you think?

Generally Bitter Admin
28,432 Posts
Discussion Starter #9
Since we're talking about oil, I've heard that once you put synthetic oil in your vehicle, you can never switch back to regular oil, even after an oil change. Not sure I believe that. What do you think?
I think that I'm half-tempted to ban you because of this question of yours. Seriously.

It's too cold here
335 Posts
Why would you ban someone for asking a question? I used to work at walmart doing oil changes and our supervisor trained us not to let people switch oils. I never really understood why and when I asked, he never even provided an answer. Would just reply with "We just can't do it."

I personally don't see where it would be so bad. But for some reason, the supervisor insisted we not let customers do it. We would have customer come in who would ask about it and our supervisor was set firm on his decision. But whatever. Nevermind. Forget I asked.

Generally Bitter Admin
28,432 Posts
Discussion Starter #11
Why would you ban someone for asking a question?
Right above your post said:
Because we have an entire forum for you to ask these type of questions in, not this one. Not to mention the damn sticky at the top of this forum. Why do I react so tersely? Because not only is said forum mentioned all over the place, in addition to the thread specifically for oil, there's an overabundance of threads in here that highlight that same sentiment as well. That's why I would "ban someone for asking a question" like yours. Did you not happen to see this giant thread, ( just above this post of yours? Do you see how irritating this could be?

It's too cold here
335 Posts
Yeah, I saw that sticky and I read that thread a few weeks back and there's actually some good info in there. I read the articles about engine temperatures, oil weight and viscosity. I read about how oil is refined and I read about the differences between synth blends and regular blends, etc., but I didn't see anything in there about recycled oils and I don't really even remember seeing anything about switching from synth to basic and back again.

Initially, this thread was a discussion about the recycled oils emerging on the markets but I decided to go ahead and throw that question in there about the synth blends. I think it's a fair enough discussion.

No need to get all bent out of shape about it. Besides, it's to be expected from people who are new here. I'm still new. I've read posts on here from members who are worse off than I. Sometimes you just gotta take it easy and say to yourself, "Hey, this guy is new. He doesn't know shit about cars. He's still learning the ropes." And cut him some slack. Now if I was in here bad mouthing people, posting inappropriate photos, or just being a basic ass towards everyone then yeah I would see good cause for banning. But I'm not doing any of those things. I do my best to respect the senior members and I thank them for their help, offer positive feedback when I think of it, and participate in other peoples threads (mostly in the lounge and members rides) instead of just starting my own all the time.

Yeah I can see how you can get pretty irritated with people on here. Specially the newbs. But I'm not intentionally trying to get on anybody's nerves. I was just trying to have a conversation.

Generally Bitter Admin
28,432 Posts
Discussion Starter #14
I'm not "bent out of shape" about a thing. People live real lives outside of a internet forum, so if you think that about me or If you have that impression of me, you're sorely mistaken because there's very few times bent out of shape can ever be said about me, and the few times that it would be correct, you'd know about it.

Now you've said it yourself:
gemini9 said:
Initially, this thread was a discussion about the recycled oils emerging on the markets...
at what point does that include recycled oil? Further, that oil thread you've read at the top is open, which means its for oil discussion.

Now with regard to new members, cutting slack, or whatever designation you want to give someone who ignores things posted around here and posts anyway, please go to the new members forum and read the doctrine of C3G. Everything is already addressed.

and I don't really even remember seeing anything about switching from synth to basic and back again.
Then there's no way you read that whole thread.

562 Posts
"Some will never be able to understand these concepts unfortunately"- chapter 1

"If while on the road you are forced to add oil there are rules. Let us say for example that our engine has synthetic Mobil One 0W-30.

Use the same type and brand if you can. If you are using Mobil 1 then it is acceptable to mix different grades but use a close grade when possible. It is not a good idea to mix say 1/2 your oil tank with 0W-30 and 1/2 with 15W-50 Mobil One.

If there is no Mobil 1 available then use mineral based oils next, preferably Mobil as first choice then any other name brand next.

The last choice is to mix a synthetic of another brand. They specifically said this should not be done in the past but most say that mixing is compatible now."

Hammer Time!
18,119 Posts
Yeah, I saw that sticky and I read that thread a few weeks back and there's actually some good info in there. I read the articles about engine temperatures, oil weight and viscosity. I read about how oil is refined and I read about the differences between synth blends and regular blends, etc., but I didn't see anything in there about recycled oils and I don't really even remember seeing anything about switching from synth to basic and back again.
pssst...check post #3

Manual Swapped!!
5,977 Posts
pssst...check post #3
There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synetics. Polyglycols don't mix with normal mineral oils.)
There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.
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