I did a drain and fill at 89,000 miles for the first time (previous owner neglected the transmission)...
Mysteriously 8 qts. came out of my trans by just opening the drain plug. So i replaced like 90% of oil with a single drain and fill. Look here:
Don't worry about mixing the oil. There's alot of people at bobistheoilguy.com doing drain & fills with SPIII and castrol IMV. They are fully compatible.
Do another drain and fill in a week or so and you'll get like 70% of new oil.
Also if you have questions about mixing the oil or any other kind of question,you can contact castrol and they answer right away. the Customer support is very nice. just fill in this form:
Sounds good! Thanks for the advice j0rg3!:fawk: