This reply will answer all three quotes above. The reason why I choose a 10W-30 over a 0W-30 is due to two important areas of engine oil performance.
1. NOACK Volatility
- true synthetic 10W-30 will have a much lower NOACK %. This means that less oil evaporates/vaporizes, and re condenses inside the PCV system. This will allow less oil to build up inside your supercharger, intake manifold, throttle body, intake valves, and combustion chamber. People who use engine lubricants with very low NOACK report less oil contamination in their oil catch cans as well. *50% less, sometimes more depending on their previous engine lubricant being used*
2. Shearing Stability
- The closer the first and second numbers are on the SAE ratings, the more shear stability a lubricant will have. True synthetic 10W-30 lubricants normally do not change viscosity at all. They contain little to no viscosity improvers that "cheat" the grade and can wear out. If you do not drive your car in freezing weather under 32*F, using a 0W lubricant is pointless. True synthetic 10W-30 will flow just as well @ 32*F as petroleum based 5W-30.
What I really like about the Mobil 1 0W-XX oils is that my vehicles seem to rev better and I have averaged what seems to be about 1 mpg better fuel mileage on all of them. My motors are super quite with these oils and the high moly additive along with low costs just adds icing on the cake. All UAOs on Bob is the oil guy for these oils seems to come back great and my OCI's are no longer than 5K, so shear is not a concern for me.