Oil pressure

[Hawklover]

Always know I am sure to get educated from this group:-)

I'm not sure what oil pressure tells you. Yes, you can put heavier oil in it, and the gauge pressure will come up, but so what? That higher pressure just means that the oil is circulating more slowly.

Actually, I think that an "idiot light" which comes on when the oil pressure is abnormally low, is just fine.

When the new Lotus V8 was introduced many years ago, the oil pressure gauge was marked L-N-H because Lotus figured owners would panic if they knew the actual oil pressure, which was about 5 psi.

If you think about it, the instantaneous pressure on rod and main bearings is at least several hundred psi, and on cam surfaces can be several thousand psi, so the oil pump pressure is almost meaningless. As long as oil is present, it is the oil film strength, not pump pressure which prevents metal-to-metal contact.

Abnormally low oil pressure can tell you that there's wear and increased clearances, but it does not indicate inadequate lubrication.

Yes, you can increase gauge pressure with thicker oil, but that does not equate to better lubrication.

[jackb]

is STP compatible with synthetic oil ?? and yes, old acidic oil will chew away at the bearings. At least to Babbit-type bearings. You will see the deformation appearing very differently than worn bearings....looks like someone took a small chisel to them...

[hank63]

I've also seen bearings that looked like metal eating mice had been at them. It was a -39 Studebaker (and I didn't buy it).

[jackb]

"As long as oil is present, it is the oil film strength, not pump pressure which prevents metal-to-metal contact".............care to comment on hi output oil pumps ??

[jnormanh]

"As long as oil is present, it is the oil film strength, not pump pressure which prevents metal-to-metal contact".............care to comment on hi output oil pumps ??

So long as a pump has enough pressure to deliver a continuous supply of oil to all contact surfaces, I believe the pressure with which it does so is immaterial. For example, splash lubricated 4-stroke, and most 2-stroke engines run with zero oil pressure, and can last a long time, as long as there is enough oil to splash around.

Think about it. Wrist pins, pistons, rings, cylinder bores and valve stems never see pressurized oil, but wear out along with the rest of the engine. Who ever tore an engine down because the wrist pins were worn out?

The highest metal-to-metal pressures are probably cam ramps, maybe rocker arm tips. They get their oil at zero psi.