Oil pressure fluctuation

[Nachos82]

A quick question for anyone out there. I was wondering if it is normal to have your oil pressure fluctuate on your truck. I am talking when cold it is around 50psi or so and after warming up it may drop to 30psi at an idle, and then during driving go back up to 50psi or so. I have always thought this to be normal, what do you guys all say about it.

[68gmsee]

My 69 Chevy used to do the same thing. (not running right now).

Pressure was always higher until it warmed up then it would go down when idling at a stop and I could rev it up and see it go up again. Ran it that way for many years with no problems- then I did an overhaul.

Wear was the problem. Redid the crank and put new bearings, rod bearings, rings, oil pump, redid the heads, etc. Still had some fluctuation but it helped quite a bit.

Depending on how many miles on your engine could be just a worn oil pump or crankshaft bearings.

[70GMCer]

That is normal........

[Longhorn Man]

30 at idle warmed up is fine
50 when cold is fine too
this is all normal

[Nachos82]

Thanks for the quick replies all, I figured it was all normal since mine trucks always done it. They are all the higher 100k+ mile stuff so that sounds good.

[Blazer1970]

Originally Posted by GMC AMI

As long as the pressure stays above 25 at slow idle when warm no prob!

It does not need to be that high at hot idle. 10 psi is fine. 5 psi will work just fine also, but that is the time to start thinking about what might come next.

[68gmsee]

Originally Posted by Blazer1970

It does not need to be that high at hot idle. 10 psi is fine. 5 psi will work just fine also, but that is the time to start thinking about what might come next.

True.. Mine was dropping pretty low on warm idle and decided to overhaul. It was running okay but was also smoking on startups.

So, if it's still running good, mileage and oil consumption are normal and it's not clattering or clunking, keep on driving...

[67ChevyRedneck]

Originally Posted by Blazer1970

It does not need to be that high at hot idle. 10 psi is fine. 5 psi will work just fine also, but that is the time to start thinking about what might come next.

Mine's been idling at 20psi hot for 4 years. It starts off around 50 when cold, drops to 20 at idle and runs from 40-50 down the road, depending on RPM.

I think your truck is fine

[ChevLoRay]

Generally, 10psi per 1000rpms is a good rule of thumb for a warmed-up engine.

My truck pegs the guage when it is cold....80+psi. When it is hot, it's less....waaaay less.

I'm into the beginnings of the thought process of getting a Goodwrench 350 longblock to relieve the 220K (or 320K) original engine in my truck. It's been built once, I was told, but not by the previous owner, who had it for nine years and I've had it for eight.

[matthufham]

i wish i would of known this with my old engine, it never got more than 12 psi. i was always burning bearings... i didn't know the oil pump was bad until my new crate 350 ran alot higher pressure.