>I added a quart of Marvel Mystery Oil to my regular (Castrol Syntec) motor >oil last time I chaged it. Way "over Kill" if you are using synthetic oil you don't need any ADDITIONAL additives, the "marvel" formula has a detergent effect that you don't need (since your ''synthetic" is taking care of it). Avi Meron 86 5Kcstq I am not always the devil's advocate, but never one to miss an opportunity....