Bob, you are right about a "thinner "
oil flowing faster than a thicker
oil. What you look for is an
oil that will flow fast at start up, and give protection at operating temps. Mobil 1 is the right choice. But it works because of its high VI(Viscosity Index). Unlike mineral oils, Mobil 1, a PAO, has a naturally high VI, and has only a small amount of a VI improver. Cross graded mineral oils have more VI improver and cannot flow as quickly as a PAO at low temps because of this, even though the viscosity rating will be the same. a 0W-30, 5W-30, or even the 15w-50 in Mobil onearegood choices. If you are doing a lot of hard driving, I would reccommend the 15W-50, but for day to day driving, the other two would be ok, with the 0W utilized in colder climates.