Oil pressure low

[Marky Dissod]

Old oil never makes as much psi as new oil. Older it gets, less psi it makes.

 

[Angelo217]

Those value look perfectly normal for the mileage you have. What does the pressure goto when cruising at 55pmh? How about idle to 35 mph? Do you have a standard 3.73 rearend?

Idk it’s like, maybe around 30 ish as of right now it’s acceptable since like I said I just did an oil change. Drove 300 miles around Galveston and Houston. HOT idle after 2 hours of driving with this fresh OC in idling just a hair above 20 PSI. Normally running idle to 35 it’ll shoot slightly above 40 psi. And it’ll run at 30 or so idling at 55 psi. Rear end not sure. It’s a z71 has the locking rear differential via traction control button. It’s a 2WD

 

[Angelo217]

Mine was recently intermittently going down to 20 psi before I replaced the oil pressure sensor. Maybe the heat when the engine is warmed up is affecting the sensor but I don't know about the new oil/old oil aspect.

Is your pressure fine now? Post sensor replacement.

 

[Angelo217]

Another reason I bring this up is by comparison.
We have a second 2006 Chevy Tahoe 5.3 L, LT trim. it’s got 300k miles on it. 160k miles of straight neglect and abuse, as it is a work truck. Now my brothers vehicle. It makes fantastic oil pressure. Around 60 on the highway no problem. Idles at 40 all day long even on old oil.

This is mainly why im concerned about mine. As mine to my knowledge did not get anywhere near that level of abuse.

And by abuse I mean complete mechanical negligence until something broke basically. Very rarely did oil changes on it. (This was not my vehicle, I take care of my vehicles lol.)

 

[petethepug]

If you overfill the oil after the motor is warmed up at idle and the pressure goes up by 5/10lb you can verify if the O ring on the oil pump is bleeding air into the system or … replace the O ring, it’s bad.

Be sure to drain extra oil out b4 u drive it. You could also swap out the oil pump and replace with a HD version.

 

[DRLexpress]

If you overfill the oil after the motor is warmed up at idle and the pressure goes up by 5/10lb you can verify if the O ring on the oil pump is bleeding air into the system or … replace the O ring, it’s bad.

Be sure to drain extra oil out b4 u drive it. You could also swap out the oil pump and replace with a HD version.

Wow, can't believe I never thought of that. How much extra oil does it take? Could you just park nose down on a hill or front wheels in a ditch, to get O-ring under oil?

 

[petethepug]

1-2qt

 

[Mudsport96]

It is also possible that the pressure spring in the pump is getting weak.

 

[mattt]

My 2004 with high mileage was doing the same thing on the original 5.3 engine. What I found out over time, is it had what started out as a very small coolant leak from a Castech head and when the oil was changed, it would return to better oil pressure. Over time, and as miles added up the oil was being compromised and polluted with just a little bit of water/coolant. As time went on, and the leak got worse, the time period of good/standard oil pressure became shorter and shorter since the oil was being compromised quicker.

When the engine is cold, pop your oil cap off and look on the underside/inside the cap. Do you have what looks like droplets? Sometimes you can even see evidence of coolant pollution in the fill tube that the cap screws into. That is what I observed and found out on my Tahoe, YMMV.

I have an old thread here from years ago asking the same thing as the original poster in this thread.

 

[Tonyrodz]

My 2004 with high mileage was doing the same thing on the original 5.3 engine. What I found out over time, is it had what started out as a very small coolant leak from a Castech head and when the oil was changed, it would return to better oil pressure. Over time, and as miles added up the oil was being compromised and polluted with just a little bit of water/coolant. As time went on, and the leak got worse, the time period of good/standard oil pressure became shorter and shorter since the oil was being compromised quicker.

When the engine is cold, pop your oil cap off and look on the underside/inside the cap. Do you have what looks like droplets? Sometimes you can even see evidence of coolant pollution in the fill tube that the cap screws into. That is what I observed and found out on my Tahoe, YMMV.

I have an old thread here from years ago asking the same thing as the original poster in this thread.

I think that's what happened to my Express van. Had the 4.8 with the 862 heads--which are known to be prone to cracks. When i sold my van the oil pressure was basically at 0.
Your oil pan might have similar sludge too.