Funny Oil Pump Activity
 

Hey guys, I got a problem with my oil pump relief valve, I think. Let me know if anyone else has had this or know why its doing this.

Recently my oil pressure relief has been purging at 30-35psi. That's not really accurate, though, because by 3000rpm it will rise to 50psi and then the needle will immediately drop to 35 and hold. As the oil is warming up everything is normal, then once it reaches temp the pressure will begin acting up without warning. Then, until I idle the engine for a few minutes, it will only ever go up to 35. Starting off again after idling for a few minutes it will shoot up to 50 and drop to 35 again.
Another detail is that when the car is warming up on a long stretch of road where I never stop the oil will warm all the way up and act normal, holding between 50 and 55 the whole time. Once I stop and take off it acts up again.
I've set a mechanical gauge up and it shows the same activity.

Blockage? Worn relief valve? Other BS?

Whats the history of the pump? Engine?

What gauge are you reading the values from? My experience with aftermarket oil pressure gauges is that most of them have very short lifespans before they start doing weird and wonky things.

--Ian

Engine rebuilt 10k ago. Pump was reused, had good pressure before.
Edit: 142k on the odometer, I'm assuming its the OG pump.

My coworker let me use his test gauge, it was either Blue-Point or Snap-On

Edit: I should add that I don't think the engine or pump is worn because the idle pressure is fine, and its able to get to 50psi in such a typical manner before it shoots down to 35. Just my thoughts.

Just tried a thicker oil (15w40), no change in attitude