PP 5w20 has a good clean base oil with good detergency, and the 0w40 version of PUP was made with assistance from FCA specifically for the 6.4. So consider that, FCA engineers can make any oil for the 6.4 hemi they want, and they choose a 40 weight. When the gov't clips their nuts because of CAFE and API garbage, they spec a 20 weight oil for the mds system and lie to everyone and say the mds requires 20 weight oil. At Ram forum we have a poll, roughly half of the forum use 30 weight or higher in the mds. So why would we bother to go out of spec? Because there is a large issue with cams and lifters needing replacement between 70k and 100k, there are threads on it, do a search. So PP is a fine product, 5w20 is nearly thin as water and not a great choice for a 390hp engine imo. Since you are in Canada, maybe 0w30 would be a great choice for ya, that would likely be the thinnest 30 weight, so that would be the closest step up from 5w20 unless you mixed. I don't even know if PP has a 0w30, but I will say 0w30 m1 is one fine product. If you get hemi tick, consider 5w30 redline, there aint none better for that.