I have a 2005 Chevy Avalanche with 218,000 miles. Oil and filter has been maintained at 3,000 mile intervals. At start, the oil pressure is in the normal range. After warm up (195 D) the oil pressure will drop if it idles down to 10psi. The low pressure alarm goes off until an increase in rpm which raises pressure. After several more minutes of running, the oil pressure is close to normal, no alarms and runs ok. There is a slight tick (possibly lifter) on the left side of the engine that has been since 75,000 miles. Should I :A- replace the engineB - Replace the oil pump, screen, flush oil panC-Let it go until motor is completely shot and replace truck / motor?

Sounds like the oil pressure bypass valve is getting ready to say bye bye, as it is part of the oil pump I would do B. Lifter might quiet down with proper pressure and flow.

Did you check the sending unit? Check it first these were notorious for going out. Make sure its not an electrical problem first then move to the mechanical! If this helped click my helpful button! Thxs!

I know this thread is quite old, but I'd like to know, did you get any resolution to this issue?

It's more than likely the o ring to the oil pick up tube. I had same problem lifter getting loud. Founda mechanic that knows what he doing. Had to change oil pan gasket and an o ring all in all bout 300.00 fix the problem. No more ticking from lifter great oil pressure. And at 305,000 miles engine runs great still geting 17 plus mpg.

I'm having same problem. I have replaced sensor, 'o' ring, oil pump, pickup tube, and cluster - still have the problem. GM is junk, stay away

My problem was fixed with the gauge cluster and oil sending unit. I had good oil pressure at idle cold, and would slowly drop to zero and only come off of zero when revving hard. No engine noise present and ran fine. I have been running about 10k miles since with no issue after changing the cluster and sending unit. What I'd suggest is connecting an oil gauge to the sending unit port and measuring the oil pressure yourself. If it's indeed low in warm idle conditions and stays that way, then you need to dig mechanical. Most people have solved the mechanical side of this issue with the oil pick up tube o-ring.