Originally Posted by TrackRat
All engines consume oil in normal operation. Some consume more than others, particularly hot running tubo engines that produce more blow-by and oil vapors to be burned thru the intake. 1 qt. consumption in 2,000-5,000 miles is very normal. If you use less than this your engine has very low oil consumption. It's completely normal to need to add oil between long OCIs.
I wouldn't be concerned at all, especially since you run the car hard. Every engine consumes a certain amount, some more than others. 1 qt./10K miles isn't bad. Early E39 M5's consumed quite a bit...and the back end of the car showed it. It was actually pretty disconcerting.
Personally, if you love the car, I'd be changing the oil earlier than every 15K miles like BMW recommends. That would alleviate this issue all together. And could potentially avoid other problems down the road as well.