What is the normal engine oil PSI of a 1990 GMC Sierra?

[sniperlif3]

Well as i said ive got a 1990 GMC Sierra, that has a 5.7L chevy 350 small block and i was wondering what the normal engine oil PSI should be... The stock gauge goes from 0 to 60 and when i first got the truck it was running halfway which is 30 PSI just checking to make sure that is the correct level...

Also if you know why the psi would drop to about 12-16 when the car is warmed up and when on the freeway for a little bit, but when i gas it the psi jumps up a bit closer to 30 again untill i let off...

 

[Molson02536]

Your oil pressure sending unit may need to be replaced and you may have to start using a higher grade oil "Thicker". Your connecting rod bearings is where you get your oil pressure from and they could just worn down and have a higher tolerance clearance now. Start with the simple and replace your oil pressure sending unit and try adding Restor or Lucas engine oil treatment to your engine. This should get you a few more years down the road.

Normal pressure in PSI would be about 60 psi at start up, and maybe 25-40 psi at idle once fully warm. At 2000 rpms- once warm- my 1996 (367,000 miles) runs about 55-60 psi. 5W-30 with Restor engine oil additive added.

The higher the RPM on the engine the higher the oil pressure should be which is created by the Main bearings and Connecting Rod bearings. A sloppy bearing will cause a drop of oil pressure. If you do drop the pan and discover a loose rod bearing, be sure to measure the crank throw with a micrometer in two perpendicular directions to check for out-of-roundness. If the crank throw is too far out of round, a new bearing will not fix the problem for long.

Start with the simple and replace the oil pressure sending unit and add some Restor or Lucas engine oil additives to help your high mile engine. Keep us posted and good luck.