What is Normal Oil Preasure ?

leftwing55 · July 20, 2005

Just bought this truck 02 GM 5.3 at idle hot it is 275 kpa and running around 400kpa.

Does that sound high. Not sure what oil the guy had in. 5w 30 or 10w 30.

allenmehrer · July 20, 2005

Idle i run 40 but when I step into her she'll give me 60-75. But then I think mine is too high! go figure.

OnBelay · July 20, 2005

Factory specs are:

OIL PRESSURE (MINIMUM-HOT)

41 kPa at 1,000 engine RPM (6 psi at 1,000 engine RPM)

124 kPa at 2,000 engine RPM (18 psi at 2,000 engine RPM)

165 kPa at 4,000 engine RPM (24 psi at 4,000 engine RPM)

+/- 15% is allowed, this assumes proper engine oil; SAE 5W-30 or 10W-30 if outside temp stays above 18'C/0'F

leftwing55 · July 20, 2005

Factory specs are:

OIL PRESSURE (MINIMUM-HOT)

41 kPa at 1,000 engine RPM (6 psi at 1,000 engine RPM)

124 kPa at 2,000 engine RPM (18 psi at 2,000 engine RPM)

165 kPa at 4,000 engine RPM (24 psi at 4,000 engine RPM)

+/- 15% is allowed, this assumes proper engine oil; SAE 5W-30 or 10W-30 if outside temp stays above 18'C/0'F

<{POST_SNAPBACK}>

So not to worry then ?? Do you think its to high ?

MrQuadrasteer · July 20, 2005

I've always heard you should have 10psi per 1000rpm.

Those factory specs sound a bit low to me. I think they do that so when folks have low pressure, they can fall back on the, "well, it's w/in factory specs.."

I would sh!t if I saw 6psi idling

I get 35~40 idling, 55~70psi running, hot.

allenmehrer · July 20, 2005

what would an abnormally high oil pressure mean as far as something going wrong?

MrQuadrasteer · July 20, 2005

The oil could squirt right past the rockers and not lube them, it can blow seals here and there, it might also indicate a blockage somewhere in the oil passages....

biochemist · July 20, 2005

Hi there, ~40 idle, @ 75 MPH ~57 , later,

OnBelay · July 21, 2005

I've always heard you should have 10psi per 1000rpm.

Those factory specs sound a bit low to me. I think they do that so when folks have low pressure, they can fall back on the, "well, it's w/in factory specs.."

I would sh!t if I saw 6psi idling

I get 35~40 idling, 55~70psi running, hot.

<{POST_SNAPBACK}>

Well, those are the MINIMUM factory specs, and also allows 15% over that. If you are depending on the factory guage on the dash, hook up a real, mechanical pressure guage and see what it reads. Most factory guages are off by at least 25%, and read high.

I don't care what you heard or why you s**t, that's what GM says the pressure is supposed to be. It looks to me like the man who asked the question got his answer-his oil pressure is abnormally high. Since it is not known if proper oil is in place, first thing I would do is change oil to proper weight with a good filter (Purolator or Delco, no Fram crap) , run 1000 miles, then change again. This would give you best chance for having only proper weight oil in the engine.

I most frequently see too high pressure caused by restrictive oil filters and improper installation of the filter-either too loose or too tight, and the oil pump flow is restricted. Amazing what those quick lube morons can do to screw up a simple job, especially with the cheap filters they use.

With all that said, it's worth your time to get a "real" reading of the pressure. If you have the proper oil and other factors mentioned above are in line, the potential damage of pressure that high will really depend on the type of use the engine gets. Running around town, frequent starts and stops, you'll have lubrication issues over time. If you do mostly highway driving, assuming a good warmup and not instant sustained high rpm, you probably won't see a lot of problems from high oil pressure.

MrQuadrasteer · July 21, 2005

Whatever, Belay. I've built enough engines to know 6psi sucks. If you're comfortable with, have at it.

And we all know GM never lies

Raymond Lowe · July 21, 2005

My oil pressure gauge reads about the 3/4 mark on the gauge cold. A slight bit higher if it's new oil (Mobil 1 5W30).

When it was new, coming off the freeway with a hot engine, it would be around the halfway mark at idle. Now, with 225,000km(140,000mi) it's just getting down to the 1/4 mark at hot idle, still well above the red bars. This is a the normal progression you should see as the bearings wear. ie; very little change in cold pressure and progressively lower hot pressure at idle over the service life of the engine.