My '03 3.0 took 7.5 litres (8 US quarts) if I let it drain fully. Depends pretty much on how long you leave it to drain, if the oil was warm, etc.

The DIY on this site states 7.5 US quarts, but it is always better to put in a little less and then check it. The correct amount isn't 7.5 or 8, it is the amount that takes it to the full mark on the dipstick.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue