i just got my new engine (7k miles) and am going to hook up the sds. my question is when can i change over to synthetic oil? i've heard i have to wait until the engine is completely broken in. . but i'm not sure how many miles it takes. also, do i have to brake in the sds with conventional oil or can it run off of synthetic from the door? should i use a different weight rather than 5w30 since i'm fi now or no?