Rednucleus

05 Suburban 5.3l 250k miles; runs well, not using significant oil; normal maintenance intervals by trusted mechanic.
In the last few months the gauge reads 20 psi at both cold idle startup and standard driving rpm's. Once warmed up, idle psi goes up to 30 & driving psi 40-45. This is the opposite of all my past experiences - for instance my '93 with 350k has cold start 45psi, drops to 10 when warm.
My question is why is pressure going up at operating temp vs cold when in my experience - especially with all other hi mileage motors - has been the opposite? I have seen posts about a clogged filter at the oil p sensor - does my motor have this and could the hot oil better get through 250k worth of goo to explain what I am seeing?

kevinkpk

RPM has everything to do with pressure. Yes, warm vrs. cold the viscosity is lower, and lower pressure. Another thing is the oil. I have an 03 with 200+k, am using a FS (valvoline) high mileage, I am seeing the same results you have.

Rednucleus

So in this case, why is my pressure higher when oil is hotter - it should drop as it heats up, mine goes up

kevinkpk

What oil are you using? High mileage I use, this reversed the issue, same viscosity 5-30. Even as the oil temp rises it maintains the same (per rpm) pressure

tech2

that does defy science. I can only speculate.
At least your getting the min pressure of 10psi per 1000rpm

Rednucleus

Does my '05 have this part and if it's becoming clogged up would it explain what I am seeing?
https://chevroletforum.com/forum/tah...=sensor+screen

tech2

pretty sure the screen is only on 07 to 14 5.3's

Rednucleus

Oh well; wife had scheduled service last week. Drove it yesterday, back to normal. Idles 35-40, highway 45-55 psi. See what the future holds!

Rednucleus

And now - gauge sits at 80 psi all the time! All others are normal operation.

tech2

would be nice to be able to put a oil pressure gauge on the engine to verify the acutual pressures. Gm dealers have an adapter housing that screws onto the oil filter adapter housing...making pressure checks quick. This allows direct comparison of the trucks guage and the "master gauge".
-if the master gauge is reading normal...the issue is isolated to the trucks sending unit, wiring or gauge.
-if both readings are the same...the issue is oil pump or engine related.

if your gauge needle is not moving engine is off or on...maybe a cluster stepper motor. youtube gm stepper motors cluster repair and you can see the problems others are having and the cheap and easy fix.