Originally Posted by 808MGuy
I'm starting to wonder what the oil sensors are looking for when it gives a recommended change interval. Is it testing for some kind of foriegn content or just viscosity?
I don't think it is actively sampling the oil at all to suggest the change interval.
I think the interval it suggests is based on fuel burn. That is the parameter that the pre-E9X cars used. Burn a lot of gas or do a lot of city driving, and you get shorter intervals.
The GM way had something to do with measuring the capacitance of the oil, but I don't think the BMW system works like that.