I know there is a great debate about what oil to use. A guy on a motorcycle forum sent his oil off for analysis and I thought some of you here might appriciate the info. This was a sample of Rotella T6 15W40 deisel engine oil with 4K miles of commuting and alot spirited canyon riding. The zinc content looks pretty high. I may give it a whirl in my car. I don't know if was T6 but I used their full synthetic in my motorcycle for a couple of oil changes. I switch back to regular bike oil because I think my clutch was slipping.