erratic oil pressure AC Delco Filter / GC

[sub_zero]

Well the truck was coming close to the Life monitor change interval - I had planned to run two intervals owing to the use of quality oil. Well I couldn't do it my oil pressure once fully warm was low at idle and just erratic at highway running speed hunting 150 kPa for absolutly no reason. I've change both oil and filter now (NAPA / XD-3 0W30) and the problem is gone. I suspect it was oil filter related. Is the pressure tapping before or after the filter? Does the internal bypass valve leave a signature on oil pressure when it lifts? Comments?

 

[427Z06]

Year, make, model, engine would help in the diagnosis. Previous oil and filter?

 

[sub_zero]

It's a 2000 GMC Sierra 5.3L 4X4, Have run Castrol Syntec 0W30, Pennz 5w30, XD-3 0W30 and Formula Shell 5W30 before. All with either NAPA Gold or AC Delco filter. Haven't seen this problem though.

 

[Hirev]

How many miles on the oil and filter? How many miles on motor? Do you drive much on dusty roads? If I calculated right that was only 23 psi on the highway that would be extremely low. What is you normal oil pressure?

 

[sub_zero]

quote:

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Originally posted by Hirev:
How many miles on the oil and filter? How many miles on motor? Do you drive much on dusty roads? If I calculated right that was only 23 psi on the highway that would be extremely low. What is you normal oil pressure?

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approx. 5000km on the oil and filter.

154000km on the engine.

Not much dust where I drive, every now and then I drive out to the oil patch but that's it.

To clarify the actual oil pressure: Engine hunts between 40 and 60 psi, the swing was in excess of 15 psi. Occurs during steady engine speed - fully warm, on the highway. Just bloody aggravating.