Originally Posted by AlanAZ
I've been happy with M1 on this car, and my previous E46, but at the next change I'm changing to GC 0W30. I've been under the impression that M1 0W40 was a Group IV PAO oil, based on what I had read, but now I believe it is hybrid of Group 3 & 4, while GC is a true Group IV. Probably no big deal based on my change interval, still I want the best oil I can get that's approved by BMW. And I live in one of the hottest populated places on earth.
Everything these days is a blend, and Group III/III+ is a heck of a lot better than it was a decade ago. Group III oils would protect our N52s just fine end of sentence, unless you want to run extended intervals or just like the peace of mind of syn. The challenge is handling really cold winter temps but still meeting ACEA A3. You're still going to need a syn for that.
No one on e90post knows this, but I've said a hundred times - don't get hung up on looking for this group or that group. They are ALL blends. Go for the product that gets the job done. Group IV oils don't even make good lubricants without splashes of group I, III and/or V. Group IV oils are typically non-polar and don't dissolve additive packs. They're also not good for seals.
I believe that GC is a blend of III or III+, IV and V. There's definitely group V in GC because displays incompatibility with Auto-RX, which is composed entirely of esters.
Regardless, I prefer GC over M1 at the moment too because of the noise issue. Of course my "new" 2007 E90 was serviced at dealer intervals (every other car I looked at was that or even worse) and I was tempted to go with M1 0W40 due to M1's reputation for more aggressive cleaning. I still have a year of a transferable extended warranty so I didn't want to go to Redline (which having lots of group V should be pretty much the tops in terms of cleaning) since it doesn't have an LL-01 badge. I went with GC because a local store put it 40% off the day I went out to grab oil.
I bet you really would have noticed your E46 being quieter with something other than M1 in there.