I've been using 5/30 since walmart doesn't carry 0/30, doesn't really matter though since the 30 and 40 is the viscosity of the oil when it warms up. I'm guessing the spec 0w30 for the 6.1s for easier start ups? tighter tolerances maybe? not sure why they'd want it so thin though
I think the spec for the 6.1L is 0w40. Personally, I wouldn't go lighter unless you are in abnormally cold temps.
There is that potential. The oil film thickness on critical parts has a potential to be lower...which could be an issue at higher engine speeds. Oil consumption could be higher. The only ones that may know for our engines are the SRT engineers...if they even used a different oil during development.
I went back to Mobil1 0w40 from Amsoil 5W40. I am most likely hallunicating but I swear it is quieter after switching back and forth twice. Or maybe I was just really hung over twice
Put 0w40 in it last weekend and didn't really notice a different for around town driving or performance. Not to say there is a difference but I didn't notice one.