Well, after sitting on the fence for way too long I put GC green in my beloved Bimmer. Up till now she's grazed on M1 0w/40 exclusivly. I had no qualms about putting the stuff in my '05 Chevy work truck - hey, if it ruined the engine in it, BFD, the Chevy's expendible. But now I'm using the stuff in something I really care about. Initial impressions are mixed: the car drives about the same (let's face it - M1's 0w/40 is a hard act to follow), no new found smoothness or power increase that I could tell. Now the work truck is a different story: BIG DIFFERENCE! So anyway, I'll report back as I pour the miles on the car - I'm not too worried I guess, it says "BMW recommends Castrol" right on the engine valve cover and the GC is, after all an A3 rated oil with BMW's blessing right on the bottle: "meets BMW longlife-01". If does right by my 330ci, the next stop is the wife's '05 Mazda Miata! Cheers all!