I purchased a CPO'd '08 E91 last May. Last June, I had the oil changed at the dealer and they reset the oil service indicator. Since June, I've put about 6500 miles on the car (I drive a lot) and the oil service indicator reads 12,000. Shouldn't it read closer to 8500? Since I plan to do 7500 mile oil changes on this car (along with 2 year brake fluid flushes), I'm not really concerned with what the CBS indicates, but shouldn't it reflect mileage reality?
Not totally mileage-dependent The scheme they use is not (completely) mileage-based. It also incorporates engine starts, average speed, temps, etc (if you google around you can find it) or similar stuff and sets the oil-change intervals dynamically depending upon how hard the car is driven. If you were driving 5 miles to/fro work at slow speeds, it will be 15K or less.
One way to get the interval to drop fast is to track your car. I did two track weekends in October and my service interval fell from 11,500 to 8,500. I might not have had the perfect line every lap, but I didn't put on that many miles! At any rate, it's irrelevant because I changed the oil before each weekend. Cheap insurance considering the high revs.
Yeah, after I posted this I had the thought that there might be an adaptive algorithm at work here. It probably starts to count down faster the longer the current oil change stays in the car due to the accumulated wear on the oil.
