I've had some weird occurences with my oil pressure. 305 tpi, 5/speed 88'. When I first got it, start up and cruising, like 60mph or more-ish, the oil psi was 30, then after driving for awhile (car is warmed up), come to a stop, pressure will drop down to half way into that red line thing.. which I assume is bad. After I did an oil change, i put 10w-30 castrol gtx oil in it, the oil before was like 20w-or30w-50 mobil 1 or something stupidly high like that, the pressure actually went up, so that at start up and through most driving at any speed, pressure was 60-ish, higher than 60 right after start up. Idle, at stop lights(after driving for awhile), would be 30. Never going below 30. Then recently it went back to the old ways, starting up at just above 30, moving down to below 30, and only being 30 at 55mph or good bit o' acceleration. But, after its warmed up, and idle, the pressure plummets at the bottom the red, and then the motor suddenly runs very ruff. This recent running is right after I replaced all the valve stem seals. I no doubt have the rockers too tight and will adress that right now, but it was doing this problem, minus the ruff running, before all this.

But right now, it has only did that ruff running once, afterwards it's idleing at the line before red. BUT, when I turn on my heater/ac the oil pressure plummets again, and brings on the ruff running. What the hell is all this about? I think I may have an intake leak too it that's anything.

Car has 170k miles

 

have you verified PSI with a mechanical guage? Our Oil pressure senders are known o go on the fritz

 

double check with mechanical gauge.


10psi per 1000RPM is the general rule of thumb.


Its not uncommon for it to drop slightly into the red on a hot day at idle.

 

But does that explain why it would run rough with the heater on or when it was at idle?

 

I did almost check it mechanically in my school shop but I couldn't find the right guage and adapter, so right now i'm not sure what guage and adapter to use. And that's reassuring that it drops into red on a hot day, cause I thought I was alone in the world and was about to freak out. My 87' 2.8L never drops like that, but this 88 tpi likes to.