Given that most full synthetic 5w20's have a lower VI and often a lower volatility, do you think they are a better alternative than your 0w20 full synthetic? Other factors though include the type of 0w20, for example M1 EP 0w20 is majority PAO. Mobil 1 5w20 has a VII of only 160, likely little VII's. I've seen several UOA's where the 5w20's held their viscosity better than the 0w20's, but again this could be brand specific. You'd also have to really compare the base oil blend to know whether one oil has more VII's than another as some base oils inherently have a natural higher VI. We have been seeing quite a few UOA's with high fuel dilution, which we know impacts the oils ability to maintain viscosity and wear protection. My commute to work now is 3 miles on the way there, and 1.8 on the way home. It's pretty brutal. I may actually sample the M1 5w20 on my next change, which will likely be in late spring when I install the Fumoto. There won't be many miles on the oil however.