yesterday while driving down interstate lost all oil pressure and blew out about 2 1/2 qts. (undercarriage and rear doors now rustproof) gauge never moved until i realized i was smoking like crazy and stopped. sending unit went bad and oil just pumped up and out of unit. decided to replace with manual gauge (sun pro). changed what was left of oil in engine and filter. at cold engine 60 psi idle up to 75 psi driving. when warmed up 50 psi idle to 65 psi driving. later today with some extending mileage and highway time pressure dropping to 26 psi idle and quickly moves to 50 psi at driving. is this kind of pressure swing okay, or did i do some damage? engine was running a little warmer today as well. i know oil pressure changes with rpm and temperature but that is a pretty big swing and i cannot find anywhere that gives me a clear indication of safe minimum oil pressure at idle. 3.9 v6 1995 202,000 miles

 

It is said as long as you have 10 psi for every 1000 rpm you are good to go.

Is your Gauge mechanical? Hollow oil filled tube to back of gauge? Or just electric?

My mechanical Equus gauge never goes above 68 PSI. I assume that is the relief valve psi on my la 318.

At 65 mph it will read 54 psi +/- 3psi depending on outside temp.

It will go as low as 18 PSI at idle after a long freeway drive.

 

it is mechanical. hollow oil filled tube to back. i had an 89 318 that was around 20 at idle real warm but this being a v6 i wanted to make sure. dropping from around 50 cold idle to 26-27 hot just seemed big to me. thanks for the reply

 

According to the Haynes book, absolute minimum at idle is 8 PSI.
Operating pressure should be anywhere from 30 to 80 PSI at 2,000 RPMs.