What’s up guys! I’m new to this Forum, came on here for your feedback. I recently got a 2008 Chevy Silverado with the 4.8 in it. I am experiencing low oil pressure after the truck warms up. Starts off in the morning around 40-42 then as truck warms up, drops all the way to 10psi. Truck runs perfect though, No low oil pressure light or signal on the dash, cluster is just reading 10-12 psi as truck warms up. I have changed the oil and used Mobile 1 filter, even bumped the oil up to 10w 30 instead of 5w 30. Replaced oil sending unit and screen. Dropped oil pan and replaced pickup tube and O ring. What else can i do? Appreciate all the help!

 

I wouldn't mess with the viscosity of the oil. How many miles? Original owner (guessing not)? Have you used an OBD II scanner yet?

 

i just got the truck, supposedly rebuilt motor with 65k on it. Dash says 243xxx so who actually knows. All gaskets and motor mounts look new, but that means nothing. I have used OBD II and zero codes.

 

Back in the day, lots of AMC-built Jeeps would show 10 PSI at idle, but that was 40 plus years ago. It is possible your oil pressure sensor is the issue. The only way to know is put a mechanical gauge on it or install a new sender. As long as the motor sounds fine, it's probably a faulty oil pressure sensor, IMO. One word of caution is to change out all the fluids, as a rebuilt motor, doesn't mean the first owner ever did any of that. My old 1998 Chevy K-1500 runs 55-60 PSI cold and 35-40 PSI idling while hot.

 

Ive replaced the sender and nothing changed. Also changed the screen, but while putting the new screen in. It’s like the sender wouldn’t screw in all the way. It’s tight but the washer below the sender moves. Is that normal?

 

I don't know, as my oil pressure sender is not like yours. Doesn't sound normal, but things have changed over the years. Are you sure the entire motor was rebuilt to original specifications? Do you have any proof that it was, like paperwork of some kind? If not, you could be the victim of fraud, or a mechanic who cut corners. At this point, I would perform a dry and wet compression test. If it's not up to par, then you *may* have been ripped-off.