Low Oil Pressure on Longer Drives

[Jfarm]

Paragraphs!

Can you be more explicit on “changing the oil on time”; is that by the OLM, 10k, 5k, or what? Reason I ask is it has a big input in sludge formation.

I would do the easy diagnostic test as suggested by @swathdiver because at that age and mileage the O-ring is highly suspect.

2wd or 4wd? That has a large impact on how big a deal dropping the pan is.

I run 5w30 conventional so I change it every 3000 miles. I do have 4wd so It would be a pain to drop the pan. If I don't find any sludge in the pan with the camera, I will try two extra quarts of oil and seeing if I get the same problem.

Another thing that might be helpful is that after my two hour drive last week, I changed the oil immediately before leaving. After getting to my destination, the next day I changed my oil again and I was two quarts low. Not sure what that might indicate. Again, appreciate the input. I'm stumped and hoping to finally figure out the cause of the issue.

 

[Bill 1960]

I wouldn’t expect any sludge with a 3k OCI. Are you seeing any smoke to accompany the excessive oil consumption?

The most curious thing is your hot oil pressure is higher than cold. That’s backwards from normal.

 

[Jfarm]

I wouldn’t expect any sludge with a 3k OCI. Are you seeing any smoke to accompany the excessive oil consumption?

The most curious thing is your hot oil pressure is higher than cold. That’s backwards from normal.

Haven't seen any smoke. When I got my oil changed at the beginning and he said I had sludge in my filter, I was astonished. Changing the oil regularly has always been important to me. A wise man once told me that gas starts the truck but oil keeps it going.

I have not been seeing any sludge coming from the oil changes since replacing the pcv valve and oil pressure sensor connector. However, I do not know yet if there still could be sludge sitting at the bottom of the oil pan. I knew that the old truck burned some oil but two quarts low in 120 miles seems odd. Not sure how/if it could be connected to the low pressure.

Furthermore, it is very strange that I am getting the opposite of normal oil pressures. Maybe a seal doesn't hold when cold but as it warms up and gets lubricated it starts to hold better? Maybe the o-ring? Throwing ideas out there. Truck runs absolutely perfect but when I take it on the interstate she starts dropping pressure after awhile. This whole issue baffles me.

 

[rayra]

All, appreciate the input. I forgot to mention that I did put an oil additive in during my second oil change. With all this being said, I believe it may be inevitable and I have to drop the oil pan to check for sludge, bad o-ring, etc... However, if I drop the oil pan, should I just replace the oil pump while I am down there? Is there anything else that I should look at while I'm in there?

The oil pump is in the front, not in the pan. getting warm the pressures should DROP, not raise. Runs some flush. And find a better mechanic, as repeatedly changing the pressure switch is not a cure for anything except mistaken readings do to the aforementioned sludge.
You say nothing about temps, evnironment or engine, nothing about the oil type and brand you are running.

I'm running the spec'd 5w-30, have problems with a sticking lifter every 3-4 oil changes that I remedy with flush. Have about 160k mi on my '02.

And as for system oil pressure, GM doesn't even consider the pressure low on these engines until they hit single digits. Your 260k mi almost certainly could use an oil pump replacement. And many other things.
DO NOT put in an extra 2qts. The o-ring on the pickup will indeed need changed. It isn't difficult to do, after dropping the pan.

 

[corvette744]

Haven't seen any smoke. When I got my oil changed at the beginning and he said I had sludge in my filter, I was astonished. Changing the oil regularly has always been important to me. A wise man once told me that gas starts the truck but oil keeps it going.

I have not been seeing any sludge coming from the oil changes since replacing the pcv valve and oil pressure sensor connector. However, I do not know yet if there still could be sludge sitting at the bottom of the oil pan. I knew that the old truck burned some oil but two quarts low in 120 miles seems odd. Not sure how/if it could be connected to the low pressure.

Furthermore, it is very strange that I am getting the opposite of normal oil pressures. Maybe a seal doesn't hold when cold but as it warms up and gets lubricated it starts to hold better? Maybe the o-ring? Throwing ideas out there. Truck runs absolutely perfect but when I take it on the interstate she starts dropping pressure after awhile. This whole issue baffles me.

2 quarts of oil in 120 miles is extreme engine problem.If no major leak under truck then its eating it.I would guess oil control rings or valve guide seals.Has to go somewhere.So their is no smoke coming out of tailpipe i find this hard to believe.Plus reverify the pcv valve is working correctly you seem to have a few problems going on at once.If still not sure i would be doing a compression test and peek at every plug when their out.2 quarts in 120 miles is shocking.

 

[2006Tahoe2WD]

Jumping on here. I have 45psi when hot at 2000 rpm. 170,000 miles. Is that amount of pressure low? My Tahoe is a 2006 2 wheel drive. How much work/risk is there to pulling the pan and changing the O ring? How about the oil pump and timing set?

 

[Tonyrodz]

Jumping on here. I have 45psi when hot at 2000 rpm. 170,000 miles. Is that amount of pressure low? My Tahoe is a 2006 2 wheel drive. How much work/risk is there to pulling the pan and changing the O ring? How about the oil pump and timing set?

Imo 45 psi hot is pretty good.

 

[2006Tahoe2WD]

Imo 45 psi hot is pretty good.

Thanks, I'll not panic for now.

 

[SnowDrifter]

Jumping on here. I have 45psi when hot at 2000 rpm. 170,000 miles. Is that amount of pressure low? My Tahoe is a 2006 2 wheel drive. How much work/risk is there to pulling the pan and changing the O ring? How about the oil pump and timing set?

That's about right for a stock oil system

Nothing to worry about there

Mine's 65 under same conditions but I also have a high volume pump in mine

 

[2006Tahoe2WD]

okay, good. I now need to keep an eye on the rear axle. There is a whine (not loud) at 45-50mph. The noise is there at torque on and off. If held just neutral then the noise goes away. The axles were pulled out about 4? years ago and the wheel bearing inner races were not looking great - about 1/2 worn. There's always something.