It's Mobil1, not Mobile 1. It comes in 0W-40, 0W-30, 5W-30, 10W-30, and 15w-50. If you're using a different viscosity you're not using Mobil1
synthetic! You should use the lightest viscosity which gives you the
oil pressure you need (to get more flow and thus more cooling).
If you don't believe me go to their web site
www.mobil1.com .
Avoid racing oils on the street, they are not designed for the day to day conditions of a street engine.
Bob