Originally Posted By: mongo161
Just think of the drivers, under the assumption that they have M1 synthetic oil in the crankcase, have been extending their OCI to 10K or 15K. If all these vehicles have in the sump is some generic conventional oil, and they are under the assumption that they received M1, there may be some really sludged up engines on the horizon!
If the shop showed the owner M1 EP with the guaranteed 15k extended performance on the label and that owner then decided to ditch the old 3k rule and get the most out of synthetic oil, I agree, there may be a problem, but I bet you they OVERCHARGED for synthetic oil but still put on a "come back in 3k miles" sticker on the windshield. HAHA