Originally Posted by JCL

I do services generally according to the maintenance lights, usually slightly earlier. Lights have been calling for service at 28,000 km (up from 25,000 km baseline due to our usage characteristics) but I do it at 20-24k, or 2 years, whichever comes first.

Same service practices for our last five BMW vehicles. This one has 110,000 on it. No oil consumption between services, since I sold the X5 (and it seemed to be related to being a heavier vehicle, since all five vehicles were inline 6 models).

I only use BMW 5w-30 now, but have used Castrol in the past. Only OE filters. Used Mobil 1 once or twice. Full synthetic, not the Syntec Blend. Don't buy the 'Castrol isn't a synthetic' argument. Mobil lost that court case, and it was a nuisance lawsuit anyway.

No sludge. None. Inspected.

We live downtown. Some short trips, but balanced out with highway trips occasionally.

I think that changing the oil every 3-5k is a waste of money, unless the vehicle only sees that mileage every 24 months, in which case getting the acids out of the sump can't hurt.