Oh yeah... Because I realize saying that "it's fine" to run a high pressure pump without any data is anecdotal at best and misleading at worst...
Have an oil test from my rig.
Melling m295hv pump w/ the high pressure spring. I don't remember exactly which spring I used.. I could dig it up if needed. Edit: I used the red spring. IIRC it's 70psi. Oil pressure at hot idle is 48-50psi.
Castol 0w40 euro spec, Fram XG3695 (long can, sits flush with the bottom of the oil pan) and a pcv oil catch. I used to run my engine 1qt overfilled on oil out of an abundance of caution - oil drainback from the heads to the pan. Wasn't sure if the extra volume pushed around by the pump would cause an issue at higher RPMs, but that's never been realized. The oil oil sensor on my rig is a great early warning for that, but I've never had it go off, even cranking up a mountain pass at 4k rpm for 8 minutes straight.
My thought process: More oil is literally not a bad thing. Within reason, for every hydraulic system ever, flow > pressure. But in this case, more flow requires more pressure to push it. So I went high volume with the high pressure spring.
Knowing that:
- As engines wear, tolerances go up, the effective orifice increases, therefore pressure at a given flow rate will drop. So I went high volume. However, high volume without a stiffer spring just circulates it around the oil pan from the oil pump bypass, so I threw the high pressure spring too. I figure it'll keep things happy as parts wear.
- Lifters in our rigs really have a lower tolerance limit of ~27psi at idle. I have no data on this other than reading a LOT of threads of folks complaining about lifter noise, and noting what their oil pressure at idle is. So, that was a deciding factor as well
- GM's spec is stupid. Was was it.. 6psi at 1000rpm? Something like that? I'm wholly convinced that was a warranty-refusal spec. I've not seen a single engine go on to live a long and healthy life with that.
- Cold starts are mean on an engine. Oil's difficult to pump when cold. Anything I can do to get that precious fluid to the far side of the engine sooner is a win.
- By that same token, I don't believe in summer/winter oils. The very tl;dr, higher VII (say 0w30) is better than lower VII (10w30) because it doesn't get as thick when it's cold, and doesn't get as thin when it's hot. It's effectively more resistant to thinning/thickening.
- I settled on castrol euro spec 0w40 after cruising through the BITOG nerdery. Engine seemed happy. That, along with the oil pump - I have no audible piston slap at idle. Though, unfortunately, that oil is getting difficult to find these days
- The only verifiable issues I've read from high pressure oil pumps are when they're driven by the cam gear. In particular, when driven by a brass gear. Those don't like the extra shear force. Since ours are spun directly off the crankshaft, that wasn't on my radar
Mindless drivel out of the way... Here have my oil test
