Originally Posted By: ARCOgraphite
This is an 8 qt sump? Oil temp determines the viscosity. Whats your sump temp? You are likely in situ at 9 or 10 cst warmed. 5w20EP should be fine. I had the older engine in a bullitt and it got real doggy on 5w30. Slow to rev and down on power. At least your mechanical VVT should not be vis sensitive. These have non hydraulic VVT IIRC, yes?
Maybe move up in grade after the engine loosens up after 30K miles.
I see this all the time but if sump is at 200F and coolant, block, crank shaft etc are at 230F, you can bet the oil is all but instantly heated to 230F once pumped into the oil galleys... This is why I'll never use a 5W-20 in any of my engines(two 4.6 Fords incl)...