Become a fan.....20W50 unless you live in a really cold climate, like snow. Or if you have a big problem with that, spend the $'s and buy Mobil-1 15W-50. Looked in the archives but did not find a conclusive answer. I am about to change the oil in my car and I'm considering using mobil-1 10-30. Are there any problems with this? Not a big fan of the heavier oils.