About 1990 when I was at the dealer for the normal monthly warranty work visit on my '88 109E 2.6 a same vintage 190E 2.3 pulled into the service lane with a nasty sounding ticking noise. My service advisor later told my that the car had about 25K miles, and the owner admitted to NEVER changing the oil. Of course, those cars used conventional mineral based oil and the change interval to maintain warranty coverage was 7500 or six months.

I never did ask if they warrantied any work they did or had the customer pay, but clearly this problem was the customer's own fault, and he was fully responsible.

I had an excellent working relationship with my service advisor, the shop foreman, the service manager, and the MB service rep. I did my own regular maintenance including oil changes, and it showed. Though I kept meticulous records, they never asked to see them, but none of my many problems during the warranty could ever be caused by lack of oil changes or other recommended/required maintenance.

Duke