The car only has 74,000 miles on it. To my knowledge, the water pump is original. I don't think it'* had a compression test. I'll try to get in touch with the mechanic and find out for sure whether he did a mechanical pressure test.

I know when I got the Pk Ave at around 78k, did compression test & I installed a new Carter waterpump, regardless of it needing it or not. I think I called that "summer peace of mind" replacement.
He should know how to check the pump flow, through the top rad hose though.
Knowing the psi reading on each cylinder is valuable information about engine condition.
The bonus is new spark plugs go in at the same time.

So the Aurora has been sitting at the bottom of my driveway for the past five months except for a few brief exercise runs, consistently cut short once the "LOP" warning hits. The past few days have been nice and cool (lows in the 30s and 40s and highs in the 50s and 60s) and I've been able to drive the car more than 100 miles with no LOP warnings. Also, at the suggestion of someone on the Aurora board, I replaced the pressure cap on the coolant recovery jug, which has resulted in lower operating temperatures and correspondingly higher oil pressure readings. Apparently, if the cap is not maintaining 15-18 psi pressure, the engine can run hotter than it should, which would thin out the oil. I'm not going to pronounce it as 100 percent fixed until I know I can drive it in 90+ degree heat, but this is progress.

Okay, so the pressure cap was not a 'magic bullet' fix, nor was I fully expecting it to be. Yesterday, temperatures crept back into the low 70s and my LOP warnings crept back as well but not until the outside temperature had fallen back into the upper 60s. I had two persistent LOP warnings at unusually long traffic lights during rush hour traffic with the outdoor temperature at 68 degrees and engine temperature at or slightly above 220 degrees. In both cases, engine temperature quickly fell back to slightly above 200 shortly after the light turned green and I started moving again. I also had one intermittent LOP as I was waiting to turn across a couple of lanes of traffic to get into the college where I teach. It came on for about two seconds and self-cancelled. I guess the lesson to be learned is it takes a little while at sustained high temperatures for the oil to actually thin out.

I drove the Aurora to work again today--third straight day--and had no problems. Afternoon temperatures are expected to hit the mid 70s, so it will be interesting to see how the oil pressure does. I had consistent LOP issues at or above 75 degrees with the old pressure cap in place. I've ordered a brand new ACDelco pressure cap of the exact type specified for the car. Tracking shows it'll arrive in today'* mail. We'll see if it works any better than the junkyard replacement that I snagged Sunday, which is also a Genuine GM part but off of a different model car.

While it'* progress, it'* not exactly perfection...

The car did fine on the way home this afternoon with moderate traffic and outdoor temperatures between 75 and 78. That has previously been warm enough to trigger an LOP warning. Shortly after I got home, the brand new pressure cap arrived in the mail. After I put it on, I drove the car in rush hour traffic and it maintained pressure at least as well as the junkyard cap I had gotten Sunday. Tomorrow is going to be a little warmer so I'll be able to give it yet another stress test. Of course the ultimate test will come in the spring or early summer when I drive the car in 85-90 degree heat with the air conditioning running.