Chevrolet: 1997 Z71 oil pressure, chevrolet z71, low oil pressure

Question
I have a 97 Chevrolet Z71 with a 5.7 liter 350 with 140,000 miles.  Not long ago, I was sitting at a red light and had check engine lights go off.  When I checked my gauges my oil pressure was at zero.  Since then I have changed my oil, upgrading from 5w-10 to 10w-40 high mileage, as well as adding a can of engine restore.  This boosted my oil pressure to about 20lbs at idle (sometimes a tad lower) and 40lbs max  (cool weather) on a warm engine.  My question is, what should I be looking at as a possible culprit, and should I be more concerned than I am now?

Thank you  

Answer
Low oil pressure is a serious problem. You should start by hooking up a manual oil psi guage to the motor and see if the two guages agree with one another. If the manual guage shows higher psi then your stock sending unit needs to be swapped.

If the guages agree with one another than its either a spun bearing or a problem with the oil pump.