Normal mixed driving avg about 8 litres/100km, I've seen tanks as good as 7 litres/100km and towing or track duty usually 10.5 l/100 km. I've got an M20 with a Mark D chip which as added about .5 litres/100 km. I do approx 1200km a week since I dd my car as well.
BMW 325I E30 Chumpcar Race Car
BMW 540iT M-Sport (New Family Hauler)
BMW 135i Msport Daily/track toy