It wasn't an easy victory for the returning BMW squad, however - the 911 GT3 R hybrid of Jorg Bergmeister, Richard Lietz, Marco Holzer and Martin Ragginger was holding onto a comfortable lead until a technical problem forced it to retire a few hours from the end.
M3 drivers Jorg Muller, Augusto Farfus, Uwe Alzen and Pedro Lamy didn't escape technical problems either, and nursed their car home to take the chequered flag with fourth gear missing.
BMW's second M3 GT2 - part-driven by Brit touring car hero Andy Priaulx - battled from the back of the field after a first-lap crash to take seventh overall by the chequered flag, while the Z4 GT3s took ninth and fourth.
After the disappointment of losing the flagship hybrid racer, the highest-ranked Porsche was the sixth-placed number 20 GT3 Cup S.
BMW's win - its 19th at the 'Ring - puts the squad on form for its next big test: the attack on the 24 hours of Le Mans on 11-12 June.