After driving my 2005 C-230 Kompressor some 48,000 miles (In five years), it started losing about a quart of oil every 6,500 miles. The car now has about 57,500 on it and is almost 6 years old. The oil has been changed in this engine more frequently than that recommended in the Mercedes manual. The dealership uses a synthetic oil like Mobil 1. The milage driven on it is mostly local transportation, with some long distance trips. The only aggressive driving I give this car is when I pass another auto. Is this normal oil usage for a supercharged engine? How can I determine whether I have scored pistons or excessive wear on the cylinder walls? Please help, as I am hopeful in keeping this car for another two or three years. Thank you in advance!

I don't know how long you are going in between oil changes - I normally go 5,000 miles ( Mobil 1 ) but to only need a quart every 6,500 I feel is fine.

The Mercedes manual says that an oil change is needed every 13,000 miles. I have averaged more like 8,500 between changes.