I'm not sure if this is the most appropriate thread to ask this question but here goes... I'm trying to decide between Castrol Edge 0W-30 or Castrol Edge 0W-40 for my 2010 535i. The indy shop I recently began going to used Valvoline SynPower 5W-40 MST for the last oil change. As this oil is a low-SAPS oil, and BMW LL-04 rated, I don't feel comfortable leaving it in the sump for more than 5k miles. The car is now approaching 108k miles, and the oils I've used are as follows (in chronological order): BMW TwinPower Turbo 5W-30 (dealer), Mobil 1 0W-40, Castrol Edge 0W-40. These oils followed a 10k mile OCI. I switched to Castrol Edge 0W-40 after Mobil 1 0W-40 was reformulated and lost the BMW LL-01 certification. I have been led to believe that "thinner is better" (as long as it meets the requirements of climate, driving habits, etc.) and, therefore, would prefer to go with the 0W-30 over the 0W-40 for that reason (both oils are BMW LL-01 certified). I was living in a dry, arid (desert) climate previously but recently relocated to the Seattle area. With the high ambient temperatures experienced in my previous location, it seemed almost a no-brainer to go with the 0W-40. With the more moderate temperatures I now experience, I'm wondering if switching to the 0W-30 would be better (e.g. less engine wear on starts & warmup without materially sacrificing protection)? I typically drive a 10-mile (each way) daily commute to work. Otherwise, I only drive longer distances on few occasions (weekends & holidays).