I got the dash beep for the dreaded low oil pressure issue. Car seems to run and drive fine except for the warning. Things done:
Changed to an OEM filter with Liqui moly 5w40 oil.
Replaced both pressure switches
Tested the pressure with a real gauge: fine when cold at idle (25psi), drops to (8psi) at idle when hot.
When hot, 42PSI at 3000rpms, builds quickly seems OK.
Engine seems to have no leaks.
The PCV valve is the newest revision, was replaced in 2015, no idea if it's OK or not.
I'm thinking of dropping the pan and replacing the pump. That may not be the right choice though. Since pressure builds well I'm guessing it's not the pickup. What is the smartest next step?
In the old days it was things like this: On a G60 if you got a low pressure warning, you'd change oil/filter, then do am oil pump, then the next item was to do rod bearings since if they wore out the pressure would quickly drop. After that, intermediate shaft bearings would loosen up, etc...