In Reply to: Use 15w50 mobile1 for summer? -e posted by //E36er on June 12, 2000 at 14:17:56:
I would suggest using a 5W-30 or 0W-30 synthetic. Like Luxo M3 said, the protection of a 30 weight synthetic oil is more than enough protection in any temperature. And using a 5W or 0W oil will definitely help reduce (dry) cold start-up damage. Even though the ambient temperature may be 100 degrees 15W oil will not flow near to the bearings and cam/lifters, etc. as quickly as 0W or 5W oil will.
There is no need for a 15W synthetic oil or a 50 weight synthetic oil in an M3 - period...
If you like Mobil 1 synthetic oil I suggest using their 0W-30 or 5W-30. I'm using Amsoil 0W-30 in my M3.
You will be able to tell the difference in how quickly the engine revs up when compared to the heavy 50 weight oil you are now using.