Originally Posted by elmariachi
The whole thing appears to be lack of oil pressure sufficient to lube the bearings. If they have revised the bearings and it is still happening, I say its the oil pump to blame.
Could be, but can you really blame the pump for not pumping honey? That's what it's basically doing in winter conditions
. TWS is too damn thick to pump AND lubricate bearings when cold (the colder it is, the worse it gets) IMO. And this could be happening for a minute or two EVERY freaking cold start. BMW went to the other extreme IMO. They should have spec'ed 5/40, just like the equally revvy Lamborghinis, Ferraris, etc. Or at least 5/60. Those mentioned also recommend 0/40 for winter and 10/60 for the track. Doesn't make any sense to use TWS if car will be driven normally in the middle of a Colorado winter. My extractor was having a hard time extracting the oil at 70ºF; can't imagine what it's like at freezing temperatures. That's why our engines are so loud at start up when colder; engine struggles to run the oil pump.
I'm not saying thick oil is the only cause of bearing failure as only a few engines are affected, but I'd say it's a factor when parts are marginal. And definitely causes more wear in the long run than engines running more winter friendly multigrade oils. Curious to hear what excuse BMW comes up with... if ever.