It's very strange what's happening...hopefully, someone else here has experienced similar symptoms and can point me in the right direction.

Truck: 1984 Ford Ranger 2.8L V6 engine (not the inline version)

Symptoms: Low Oil Pressure

Story: I start the truck, the oil pressure shoots up 1/4 to 1/2 (1/2 is the place it should be i believe) up the oil pressure guage. From there it slowly drops, but never bottoms out? It drops into the area either right at the very bottom of the guage in the normal range (literally the white line that defines the start of the normal range), or it will drop into the tiny area just below the normal range, BUT it Never gets to the RED area of the oil pressure guage...i've driven it in this particular area for 20-30 miles, so I don't think it's hurting the engine. The thing is, it NEVER hits the RED area of the pressure guage.

What in the world would cause the oil pressure to drop after getting a good starting pressure, but not completely bottom out as it slowly decreases over the first 5 minutes of driving???

Here's what's weird about the whole thing. If the oil pressure is just below the normal line, I can rev the engine to bring it up a tinsy bit, or what really works is (since its a manual tranny), I can use the engine for engine braking, and that brings the oil pressure up slightly.

My thoughts: Bad guage? Bad oil pressure sensor? Bad oil pump? Pinched oil line? Gunk in the engine clogging the sensor or some other oil line? It leaks oil, but not enough that i think it would cause these symptoms.

I don't wanna burn up the engine...but hope to the god of ford rangers that I don't have to pull the oil pan for the third time

So far, one thing that has slightly brought up the pressure is using two bottles of STP. It brought it a fraction of the way above the bottom of the normal range. I've tried Restore engine treatment, flushing the engine with some cheap cleaning stuff, used oil patch treatment, and am on my 3rd oil filter.

 

Well, you brought up some good thoughts. Is it a bad gauge? Yes! They're all idiot lights basically.

The first thing I would do is hook up a REAL oil pressure gauge and see what it reads. Basically your oil pressure should be high when you first start the engine, then as the oil warms up the pressure will fall because the oil has become somewhat thinner.

As you rev the engine, the pressure should rise as the oil gets pumped at a greater velocity.

I would hook up an oil pressure gauge and see what is actually happening in the engine. Let the engine warm up and see if the pressure drops. Rev the engine and see if the pressure rises.

DO NOT trust the OEM gauge to tell you what is happening. I wouldn't add STP either to "fix" something that may not even be broke. You won't really know what is going on till you get a good gauge on there.

And yes, a bad sending unit could also be a possiblity.

Find out what the low and high side of the oil pressure should be, and then see what a gauge reads. That will tell you if you have problems or not.

 

How hard is it to install an aftermarket oil pressure guage? Are they readily available at most auto parts stores?

 

They're not that hard to install. I like the electronic ones because they do not have an oil line coming right into the cab Just make sure you get a good one though. If you want a mechanical one, use copper tubing for the oil, not the plastic crap.

However, you can hook a gauge right up to the engine. Do you know anyone with a gauge or have a trusted mechanic that has one? This would probably be the easiest way to get the readings. Though, if you want a permanent gauge in the truck, you can go that route as well. You'll probably need a different sending unit though for an aftermarket gauge, but I'm not sure.

You also need to find out what the min/max oil pressure should be for your truck.