How accurate is the oil pressure gauge?

[jd21476]

I had a mechanical oil pressure gauge and it seems to read kind of high. My '73 runs fine and I just put it off that maybe the gauge was not working properly. Is this a common occurrence and is there a way to check if it is the gauge or something more serious?

[crazeetxn]

What do you consider kind of high?

[jd21476]

It seems to run in the middle but then when I rev it she will max out.

[willett]

What oil you running?
Engine cold or hot?
Which motor?

[kalbert]

It is not accurate at all. Its a pass/fail indicator more than anything. Could be that the guage is just worn out. I can't think of anything that would cause high oil pressure. Get a good quality pressure guage set and screw into one of the ports and measure what you're actually getting for pressure, then replace the dash gauge as needed. 10lbs/1000rpm is the rule of thumb, up to about 40 or 50.

[jd21476]

Yeah, thats what I figured. I pulled hte gauge out to look at the back and it looked all old and worn out.

[bnoon]

It's going to be different for every truck/gauge/engine/oil/miles out there. Pass/fail from prior experience is about right.

[jd21476]

So basically it sounds like you are all saying that if it is off or runs high then it probably is not the vehicle and more likely the sensor.

[ray_mcavoy]

Originally Posted by jd21476

So basically it sounds like you are all saying that if it is off or runs high then it probably is not the vehicle and more likely the sensor.

The factory 73 - 77 mechanical oil pressure gauges do not use a sender/sensor. They are connected directly to the engine through a length of steel tubing.

And I have to disagree with some of the others here ... I've found the factory mechanical oil pressure gauges to be quite accurate. In fact, the mechanism inside is basically the same design as you'd find in pretty much any mechanical pressure gauge (factory or aftermarket). They can get worn out and/or dirty but that usually causes the needle to catch or stick instead of reading high.

Originally Posted by kalbert

... I can't think of anything that would cause high oil pressure ...

There are actually a number of things that can cause high oil pressure. An engine with a high volume/pressure oil pump will definitely cause a high reading on the stock gauge. And like willett said, the oil you're using and engine temp will play a role too. High viscosity oil and/or low temperature will cause higher oil pressure.

[jd21476]

The engine has been beefed up a bit from stock so it may be a high volume oil pressure pump. Is there a way to verify this?

[ray_mcavoy]

Originally Posted by jd21476

The engine has been beefed up a bit from stock so it may be a high volume oil pressure pump. Is there a way to verify this?

You could hook up another gauge to see what the pressure is when the stock gauge is maxed out. That is one limitation of the stock gauge ... it only reads up to 60 psi while many aftermarket oil pressure gauges will read up to 100 psi.

It's not uncommon for a high volume/pressure pump to get the oil pressure up around 70 to 80 psi. Especially with relatively thick oil and/or an engine that isn't warmed all the way up to operating temp.

If your engine is building up over 60 psi and you want to maintain a stock looking instrument panel, there were some factory 80 psi mechanical oil pressure gauges that are a direct fit into a 73 - 77 cluster. They were typically found in medium duty trucks.

[jd21476]

Originally Posted by ray_mcavoy

You could hook up another gauge to see what the pressure is when the stock gauge is maxed out. That is one limitation of the stock gauge ... it only reads up to 60 psi while many aftermarket oil pressure gauges will read up to 100 psi.

It's not uncommon for a high volume/pressure pump to get the oil pressure up around 70 to 80 psi. Especially with relatively thick oil and/or an engine that isn't warmed all the way up to operating temp.

If your engine is building up over 60 psi and you want to maintain a stock looking instrument panel, there were some factory 80 psi mechanical oil pressure gauges that are a direct fit into a 73 - 77 cluster. They were typically found in medium duty trucks.

I will have to try that. I am not overly concerned cause the truck runs great but I would like all my gauges to run correctly.