Originally Posted By: pantygnome
Originally Posted By: Hammehead
Is it the polyolester, not he moly, that quiets the Hemy tick down?
My (non-professional) theory is that the oil pressure at idle is too low for these engines once the oil is warmed up. Today, on a not-really-hot day (69 degrees) after 15 minutes of driving I was at 31 psi idle pressure. I know technically its fine, [censored] Chrysler says 5 psi at idle is OK, but I feel like the top end doesnt get enough lubrication at ~30 psi. Just getting the engine a hundred or two RPM off idle brings pressure up to 40.
Why does this matter? Moly will plate the parts which I think will help everything stay quiet and as wear-free as possible, FOR A SHORT TIME. Extended idle times of low oil pressure will cause the moly plating to wear away, leading to the noise and presumably wear. Do that enough and you'll end up with a "permanent" ticking noise and who knows how much wear. Redline has a LOT of moly in it, so it could be working better just because there is so much that it "extends" how long you can run "low" oil pressure before it becomes an issue.
I think the thicker oil helps because it stays thicker when hot (could be proven just by watching the idle oil pressure between different oils). Get a 5W-30 with some moly and you should be good to go. So, something like PP 5W-30, PUP 5W-30, etc should be OK too, not just Redline. The Pennzoil products have the chrysler "spec" but -30 isnt spec-ed for the 5.7L Hemi in a RAM 1500. My truck has 3500 miles on it, is pretty quiet at idle running the dealers free oil (which, if their invoice can be believed, is PYB 5W-20) but I only have about 1000 miles on the oil. After 2K miles on the factory fill the engine started to sound louder at idle, but it was also during the winter as well.
What do you think is being pressure lubed that could tick that is getting plated?
Pressure (resistance to flow) relative to things like bearings, is indicative of the "head" of pressure necessary to replenish their flow-through and side leakage. It also matters in engines that have oil squirters. There are many engines (think OPE) that are simply splash lubricated.
In a positive displacement oil pump, roughly the same volume of oil is being moved for each rotation of the gear or gears regardless of the viscosity as long as you are off the pressure relief. That means if you see 40psi with Redline and 30psi with PYB 5w-20, the engine is seeing the same volume of oil through the system if the relief pressure is 80psi on the pump.
I don't think this issue is oil pressure related, assuming we are talking about the same issue, which is eventual lifter failure.
What I have heard, from my buddies at the dealership is that the 6.4L, which takes the same lifters, doesn't seem to experience the issue. It spec's 0w-40. The moly levels in the various 0w-40's is all over the map, ergo, it's unlikely this is a significant contributor. The previous SRT-spec lube, M1 0w-40, did however have higher levels of AW additives (ZDDP). But the obvious difference here seems to be viscosity. The needle bearings in the rollers on the lifters APPEAR to be the failure point. The roller starts to fail, this makes noise, eventually it locks up and wipes out the cam lobe.
It is also possible that the tick and the lifter failure are not related and the tick is simply lifter bleed-down, which is mitigated by a heavier lubricant. Since all of the Redline products are generally heavy for their grade, this is somewhat consistent with the results of their use.