Not true. Im running 5w30 pennzoil platinum and the mds never skips a beat. Same as when it was on 5w20 and the same as other rams ive driven. Ran 5w30 last summer (valvoline synpower) then 5w20 this last winter (pennzoil platinum) and now pennzoil platinum pure plus 5w30 and my engine has never sounded better. Sounded like a sewing machine with the valvoline.
Shame cause they make great oil but not for my hemi.
Probably going to try and get some PP 0w30 for this winter, if they dont make it or i cant find it ill blend 0w20 and 5w30 haha
If i was running dino oil i would stick to the recommended viscosity and oil change interval.