God, I would like to see some proof of this. FYI, I'm running Mobil 1 FS 0W-40 in my 2016 RAM 1500 5.7 HEMI. Fuel mileage is great, the engine is quiet, 35 PSI oil pressure at idle with the oil at 220F. What's not to like?
I wouldn't consider that high viscosity. It's only 3.6 HTHS and shears into the 30 Grade range immediately. I'm just dubious of 4.4 HTHS Oils that are Shear Stable in later LS and G3 Hemis.