Outside of work, I don't mess with cars much(other than my own) with one exception. A good friend owns a 1987 260E, which has been in my care EXCLUSIVELY since day one. I've performed every single scheduled service, on time, since then. The car's odometer now reads slightly over 413,000 miles. I've used several different motor oils, including MOBIL 1, and always used MB filters. As far as the 7,500 mile interval is concerned, I usually do about 4 or 5 extra oil changes per 100,000 miles, at random intervals(usually before or after a long trip). At 275,000 miles I did a complete valve job w/guides because of minor oil consumption and slightly low compression in cyl's 3 and 4. During the work I found NO sludge, very little cylinder wall wear, and only minor dis-coloration of the head casting. The oil pan on this car has never been removed so I know the bottom end has not been touched. The engine purrs so smoothly you'd never think it's got so many miles on it! The lesson I've learned is simple. Use a high quality motor oil(I've used Havoline, Castrol, Quaker State, etc...)and do the service ON TIME!!! If you love your car, it will love you back.