Oil Pressure

Can anyone tell me what the oil pressure should be at in my 94 Pontiac Transport 3800 with 104000 miles at normal operating temperature driving and at idle? And in general would that be the same for all makes and size engines? Thanks hope someone can help.

Mine in almost similar condition boasts around 40psi - 280 kPa - when new filter installed. If a Delco filter, will keep that for a loooooooooong time; if a Fram filter, will go down to 30 and less within a few weeks. When hot at idle, may be substract 10 psi from above figures.