I've read posts commenting on how the oil pressure gauge in our trucks is not really a gauge or that id doesn't actually reflect oil correct pressure.

Can someone elaborate on this please. I see mine fluctuate at times, for instance when warm it'll swing to around 25ish and when running down the road it'll be just a bit beyond 40

Looks to me that it functions as a gauge, but i trust you guys know what your talking about, i just want to know what your talking about.

 

Basically, the oil pressure "sensor" in the block is just a pressure switch. As long as it sees the minimum oil pressure, the ECM controls the position of the oil pressure gauge based on other factors (engine speed, temperature, etc). The gauge will move as these parameters change in an attempt to mimic what someone would think is correct reading. If the pressure switch sees a below minimum pressure, then it will trigger the oil pressure gauge to drop and light up the MIL.

 

A quick search:
https://www.dieseltruckresource.com/...pressure+guage

 

Thanks for that. That's what i assumed, but wanted to hear the facts.

 

The guage will register as though there is pressure and is contolled by the computer based on the engine temp and RPM as long as there is at least 6 psi actual pressure and will vary on the in dash guage. Think of it as a glorified idiot light.

The engine will not have any actuall oil pressure for at least 3 to 4 seconds when the truck is started cold, this is normal, but the in dash guage will show pressure instantly. The computer will show pressure on a cold start for up to 30 seconds before it knows that there is no oil pressure!!! One of the busses at work did not have a pressure guage but it had a kill switch, if the pressure dropped below 6psi. You had to hold an override button for at least 5 seconds or the engine would die when starting.

Actuall oil pressure can go as low as 10psi hot at idle to 80 psi at higher RPM's on a cold engine. Normal hot on most engines is around 20 at idle hot to around 50 to 65 at highway speeds hot.

 

I tried searching, but didn't try it mispelled.

 

Thanks for that too Papaduck. I find the increments on the "gauge" interesting too. I forget the first, but the mid is 40 then 110