I've noticed the oil pressure gauge on my truck seems to be reading low. It's a stock '96, 6BT with about 225,000 miles. At 55mph, it reads just a bit above 20psi. It gets to just shy of 40psi on a cold start, then drops down to around 20. I never paid all that much attention to it, but did a fair amount of work over the last year or so. It runs fine, and sounds like it always has. How accurate is the OEM gauge, and what kind of pressure readings do you folks see? Should I install a mechanical gauge on it?

 

I did discover a couple of things. It's an electrical vs mechanical gauge and the accuracy, (especially one this old), is suspect. I'll check it against a mechanical gauge. It sounds as if the sender is the most likely culprit.

 

Yes checking the factory gauges with an aftermarket mechanical one is a good call.

On my 12v powered '76 Ramcharger, the factory gauge can read 20 PSI while the Autometer oil pressure gauge I installed reads 50.

I refer to the factory gauges as Guess-o-gauges....as you have to guess if the info. they are telling you is any good.

 

Thanks, Oliver! I unplugged the factory sending unit to determine which one I have, and sprayed contact cleaner on the pigtail. Hooked a test gauge at the filter housing, and got 70 psi on a cold start. The factory gauge showed a bit over 40, leveling off just under 40 on a short drive. Could cleaning the contacts is giving me a more accurate reading on the factory gauge? At least I know I have pressure. Now I need to decide if I want to replace the sender. Easy enough to do, but do I need to?

 

I would literally just install a mechanical gauge and be done with it.
As you have just learned the OEM gauge reads the pressure to be low by 1/2 the actually #.
Could be the sending unit, the wiring, the gauge...