Re: 15,000 miles between oil changes?
If I was driving mine year-round, I'd go by the service oil recommendation given by the computer. The Germans are pretty smart about this stuff. But since I drive them summer only, I change the oil and filter before I store them for the winter. That means 10-12k of summer driving (when I just had the roadster), now that's split between two XFs. Most of the mileage is highway driving. I generally don't accelerate as hard as I can, but I do drive them briskly and occasionally at high speeds (>100 mph). I expect both to last a lot of years. BTW, I do the same with my Audi A6 2.7T and just passed 136k miles.