So I pegged the oil pressure gauge...

Yes, you read that right, mileage gauge says it has 308,000 and stuck the oil pressure gauge at full. While I was driving through Iowa yesterday from Michigan, I noticed my oil pressure gauge was reading at the top of the scale (80 PSI, in some cases bouncing past that) No problems at all, temp gauge was just below the middle of the gauge (210 F), A/C blew nice and cold the whole way, probably averaged 16 MPG during the trip, and most of the way I was running about 70-75 MPH with an engine speed of 2,200 or so, but the oil gauge managed to get pegged. The one other problem I had was a CEL that was due to a P0420 (Bank 1 catalytic converter efficiency below threshold. One of the most common ones I've seen, so I was content to erase it and continue on. It did not come back.) I babied it for a bit until I could stop and check it out. When I did, there was no major, active oil leaks, opened the oil filler cap and say a bit of smoke and fumes coming out of the valve cover, but nothing major. No joke, a smouldering cigarette would probably put out more smoke. When I restarted the engine, the gauge dropped to just a bit above zero, and went to 35 or 40 PSI at idle, the highest it got the rest of the trip was about 60 PSI. I should also mention I did have this problem before on a long road trip doing the exact same thing. I just let off the speed for a bit and it went away.

My question is 1. Has anybody else ever seen? and 2. Is it normal for the gauge to do this during extended high-speed driving? Should I be worried about this or just be happy that I seem to have a healthy engine that's putting out good oil pressure? If I should be worried about this, where should I start looking first? Oil pump? Sending unit? Gauge? Oil/filter selection? (Before anyone asks, I run the Mobil 1 stuff that's designed for high mileage engines, 10W30 at the moment, and a K&N filter.)

I had this sort of thing happen to me. It turned out to be the oil sending unit. It had cracked and oil was in the plug causing it to send screwy signals to the gauge.

The problem is almost certainly the oil pressure sending unit. Across the board, Mopar replacements are least troublesome. Sending units can read low or peg the gauge when they fail. It can take some time for a P0420 to come back. In almost all cases its the mini-cats off the manifold. I've lived with it for over 200,000 miles.

Okay, thanks for the responses guys, I'll check it out. Looks like it should be easy to get to and I shouldn't loose too much oil. I've got a '96, so no mini-cats, just a big one right before the muffler with two oxygen sensors. I'm sure that stuff didn't like my header crack and the engine running richer than it should have.

Oh no!

Okay, so the new sensor is in. It's a lifetime warranty sensor from O'reillys made by BWD (formerly Borg Warner.) I have confirmed it's the right part number. Right off the bat, my oil pressure is reading higher, both at idle and while driving (about 50 PSI and pretty stable.) Looked at the old one, didn't see a pentstar like I would expect if it was made by Chrysler, but quite a few numbers on the hex head. I'll have to run them later, but I suspect this thing may be the original OEM sensor. Didn't see any damage, the transducer hole looked like it might've been clogged with something though. I'll keep an oil on my pressure while I'm driving back to Colorado and see what it does.

Only way to confirm your actual oil pressure is with a mechanical gauge.

It's true that a mechanical gauge is the only way to know for sure, but nearly 100% of folks with a pegged gauge have a bad sensor. With a 96, the emissions are very simple. In any case, NGK O2 sensors are preferred over any other brand. You can pick them up from Amazon for about half of what NAPA wants for them. A Walker cat should do if needed.

md21722 said:

It's true that a mechanical gauge is the only way to know for sure, but nearly 100% of folks with a pegged gauge have a bad sensor. With a 96, the emissions are very simple. In any case, NGK O2 sensors are preferred over any other brand. You can pick them up from Amazon for about half of what NAPA wants for them. A Walker cat should do if needed.

Click to expand...

I understand that, my point was that they said that when the switched the gauge it read different. So... THE ONLY WAY TO KNOW WHAT YOUR CORRECT PRESSURE, IS TO USE A MECHANICAL GAUGE! That was my entire point. I DGAF where the sensors are from, when you figure out what is CORRECT.

And actually, no! if the gauge is pegged then it could be an improper ground or wire issue as well.

You may not care where sensors are from, but some people just want a quick reliable fix and Mopar/NGK are the easiest way to get there. Like I said the only way to know for sure is with a mechanical gauge. I'm not sure what your point is or how it will solve the OP's issue.

When changing out instrument panels you could go this route. I peg'd my gage to 80+ p.s.i., but not looked at. In the newer panel, not the warning lights version the gage would read 10 p.s.i. no matter the rpm mph.