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Discussion Starter · #1 ·
Hi all. Been trying to figure out a low oil issue on my brothers 2005 suburban z71 with a 5.3 and 140k on the clock. Idles at about 20 lbs of pressure, maybe a touch lower. Replaced the oil pressure sensor, didn’t help. Did the o ring, also didn’t seem to help but the old o ring was pretty brittle. I’m thinking the oil pump is the next logical step, my dad thinks it could be the relief valve. Is there anything else it could be? Prior to this happening, a shop near his college de slugded the motor, and there was a thin layer of sludge on then bottom of the pan when we removed it. Thanks in advance
 

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Synthetic oil and a good synthetic oil filter is what I'd try first.

Btw, 20 at idle and 30 to 40 at 2500 is within GM specs
 

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Discussion Starter · #3 ·
Great thanks for the info. It used to idle at around 30-40 at idle so that’s why we thought the oil pressure low. He’s ran full synthetic since he got it at 110k.
Synthetic oil and a good synthetic oil filter is what I'd try first.

Btw, 20 at idle and 30 to 40 at 2500 is within GM specs
 

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Mine was the same, and I've always used synthetic; but a couple of years ago I switched to a higher flow filter and the pressure climbed about 5 lbs at idle and highway.
 

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Even my big block idles around 20 once it warms up and cruises down the highway at 40 at about 2000-2200 RPM. Also a 2005, about 160k on the clock, always used synthetic.
 
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