I know this is likely to start a war in some forums, but please indulge my newbie question. I've just started doing my own oil changes on my E90 M3. The recommended oil for this car was Castol 10W-60. In doing some reading I see that Castol is now no longer recommended by BMW and I've also read that Shell Pennzoil Platinum 5W-40 full synthetic is recommended by some, as it might help ease the potential for the dreaded ring bearing issues in cold weather climates. My car is purely a street car and living in NC we really only get cold temperatures for maybe a week or so per year, so I'm really not so afraid of high oil viscosity giving me cold temperature lubrication issues. What's the consensus on this topic, is BMW still sticking with 10W-60, or is 5W-40 now the go-to oil choice? Any guidance would be very much appreciated!