What should the oil pressure be on an 1988 MK111?
 

Took my 1988 Mk111 in for an airconditioning problem. Whilst it was there the mechanic decided to fix an oil leak from the pressure sender. He installed an aftermarket and the oil pressure indicated in the lowest white band i.e. zero approx. after a turnpike run. Before the sender change it had been just under 20Psi. Took the car back and he installed a factory sender with the same result. The car runs normally no overheat, rattles etc, It would be very hard to get a direct reading gauge into the car (They bulit the car around the sender). Do I get an oil pump overhaul? or is this type of oil pressure normal for a turbo and my previous sender was reading high? The engine is a turbo and has 150K miles. Should I install the original sender?
Help! Bruin.

At idle the oil pressure should be somewhere around 5 psi. Above idle the pressure will generally increase about 10 psi per 1k of rpm. So say at 3000 rpm you'll probably see something around 30 psi.

That's a stock system of course. Any oil system mods (and there are several) could effect your readings. I'd find a good reputable mechanic and put a direct-read gauge on there to find out what your pump is really doing if you're concerned about it.

i get around 25 psi at idle from stock gauge. and around 45 when im driving normally.