Originally Posted by Stickygreen
I've tried all kinds of engine oils on my 2008 4.7 6spd Ram, trying to figure out what oil was best (spec is 5w20 but I expected it needed thicker oil). Truck has had the ever-loving crap beat out of it for 375k miles (currently parked bc fatigue crack in front spindle). Constant high RPM's, hard cornering when reasonably safe, and heel-toe downshifted at every opportunity. 8k mile OCI's as a farm/work truck in mild-to-scorching hot weather in summer
First 80-100k was on mostly M1 0w20 afe
Then several changes on German Castrol 0w30
Then several changes on M1 0w40
After this used pretty much every name brand/non boutique full synthetic (PP, PUP, M1, syntec, Edge, MaxLife, etc) in many different weights from 0w20 to 10w40 HM. Here's what I figured out:
-only oil that made my valvetrain louder was PP 5w20
-truck didn't like M1 oil filters...got a bit ticky
-ran smoothest/quietest (by a small margin) on PUP 5w30, M1 10w30 HM, M1 0w40, and German Castrol
-felt slightly more sluggish in warmer weather with the heavier weight oils, most noticeable with German Castrol
So what does this all mean? Absolutely nothing...all subjective and engine was replaced under lifetime powertrain warranty at over 300k due to slight oil consumption, worn rockers/cams, and partially collapsed valve springs, even though it ran about as strong as ever.
So is thicker oil better? Perhaps for a track car that sees sustained high oil temps...but with my heavily abused OHC v8 truck, it really didn't seem to matter. For all practical purposes was just as happy on M1 0w20 afe as it was on the 10w40 HM.
But you said it had the loudest VT noise on a 5/20 lube and ran quietest on a Xw30??🤔 .. and valve train wear was one of the reasons the engine was replaced.🤔.. and all those areas you cited as failing are areas where maintaining a sufficiently thick oil film is critical to prevent metal to metal contact. And we know MOFT is directly related to viscosity, soooo...🤔