Speaking from experience, (former '98.5 and current '99), both used ~1/2 litre between regular changes (Mobil 1 and Motorcraft 820S) @ ~3500 km. At first I was a bit concerned so I did some of my own research. As it turns out, it seems that "higher performance" engines are built to be "looser" (i.e. more clearance between the rings and cylinder bore) to improve performance. Still not totally convinced, I talked to a professional engine builder and he concurred that this is true. Apparently, if the engine is built too "tight", it's performance suffers (although it is less likely to use oil). Regardless, the nature of any internal combustion engine includes SOME oil consumption.
If you don't believe this, check out some of the BMW websites particularly devoted to the M5. Many owners were reporting what they also considered to be excessive oil consumption.
Maybe Terry Haines can shed more light on this subject.
Hope this helps.
