I know the 98+ trucks are idiot gauges and the 97- trucks are supposed to have "real" readings but what exactly are your alls gauges saying? And for those of you with mechanical gauges, what do they say in comparison to stock gauge? I started my truck up and got 90psi at around 800rpm, and 35F engine block. As it warmed up I was seeing lower numbers and after running a few minutes was down in the 70's. As you can see, the gauge in the cab hardly moved, and of course is no where near actual pressures..

Mine usually goes up to the 3/4 mark on the gauge and then it drops down just to the other side of it.

Good post ISX... I'll toss 2 cents into this post too. I've found another flaw in the oil pressure gauge on the Cummins. Say I start up cold and the pressure to the high side of normal as it warms up the pressure falls down just above 40 PSi on the gauge while driving and idles just a tad under the 40 PSI mark. Now just idling I can look at my ScanGauge II showing 850 or so RPM's and now kick my ECT fooler the coolant temp gauge falls to 123*F on the ScanGauge but the oil pressure goes right back up to the high mark like the engine cold but the RPM's never really changed... Like I told ISX I need to make a short video of this.

In 1998 everything went computerized so all you guys are seeing is just an on/off indicator. I don't see how it would move at all unless the computer fools you with readings based on rpm/engine temp. I have never seen mine go anywhere but where it is in the video at 40.. If your gauge does weird things when the foolers are on and off then that just further proves the whole gauge is a fooler. As long as it has pressure, the gauge shows something, though it's not related to the actual pressure. Mine is supposed to actually do something but I guess my sending unit is junk. Dodge wants $65 for it because of the gold plating they put in them. I'd like to know some real numbers on pressures though. Very interesting stuff.

When I first got my FL50 it came with an electronic gauge, that would actually move to different places based on oil pressure. Then one day the "engine check" light came on (not a CEL), and the oil gauge got all erratic, this is a Freightliner, and a fault like oil will cause the engine to shut down in 60 seconds, unless you hold a rocker switch on the dash. Any ways the smart sender failed, and Cummins replaced it under warranty with a dumb sender, the needle always goes to and stays at 60 PSI, no matter what. Cummins even had to re flash the ECM to use the new dumb sender.

When I first got my FL50 it came with an electronic gauge, that would actually move to different places based on oil pressure. Then one day the "engine check" light came on (not a CEL), and the oil gauge got all erratic, this is a Freightliner, and a fault like oil will cause the engine to shut down in 60 seconds, unless you hold a rocker switch on the dash. Any ways the smart sender failed, and Cummins replaced it under warranty with a dumb sender, the needle always goes to and stays at 60 PSI, no matter what. Cummins even had to re flash the ECM to use the new dumb sender.

now that is a true definition of jerry rigging.

I guess I can believe cummins doing something like that. Always taking the easy way out. It would be neat if below each gauge there was a digital read out about the same size as the digital odometer on 98+ trucks, and it would tell you exact numbers. Voltage, gallons left, oil psi, water temp, rpm, speed.. Maybe you all can see this on SGII. I can't use one though so I am stuck looking at my gauges. I can always dream though lol.

Thats why I installed a mechanical oil pressure gauge. They are very cheap and very easy to install and it's the life blood of the engine.

does anyone know what parameters the ecm/pcm use to post a "pressure" on the factory gauge?

Actually, it is called "Engine Protect" , and it illuminates in red ,the toggle switch says "Engine Check" on it. I think it is a good idea to have the 1 minute shut down on a commercial vehicle, I am sure alot of hired drivers could care less if the engine blew. I agree "Jerry Rigging", I was pissed when Cummins said the gauge was not going to move with fluctuation in oil pressure. I miss that gauge.

I just installed a mechanical oil pressure gauge i picked up for about $15 Canadian at the auto parts store. When i first start my truck it goes to 80psi then as it warms it drops to about 40psi at idle. For normal driving it stays at about 65psi with my truck.

Minimum Oil Pressure @ Idle: 10 psiMinimum Oil Pressure @ Rated: 30 psiRegulated Oil Pressure: 65 psiWell above the minimum, my truck runs the same numbers as yours also. It's higher when you start it since the oil is cold and takes more pressure to push it everywhere.

I need to add a gauge to mine... I also need to make a video of the Oil pressure gauge vs. ECT fooler switch...

I need to add a gauge to mine... I also need to make a video of the Oil pressure gauge vs. ECT fooler switch...

i have the edge juice w att. and it is nsync with the factory gauge...idleing at stop light in drive at full engine temp is 25 psi and going down the hiway cruise at 70 mph it is bout 63 to 65 psi...course i use lucas synthetic oil stabalizer..dunno if that helps or not.

With my mechanical gauge I get about 20-22 at idle, and 58-62 when cruising. As high as 80 with a cold block and cold oil. That's with the sender on the drivers side of the block by the ECM and Amsoil 15w-40 AME.

A little high especially at cold idle. I would try 2 quarts of 5-30 mobile 1 and 3 quarts of 15-40 or 15-50 mobile 1. They will mix and bring oil pressure down some mainly while cold. I put a 302 ford factory remanufactured engine in my 68 and it came with recommended 15-40 shell rotunda for diesel for cam breakin. Also anything that will keep a diesel clean is good so that is what I use.

Well I finally remembered to film a clip of video of the 24V and the effects of coolant temp vs oil pressure...

good video! that is why i call these "dummy" gauges. they are set by the computer rather than what it really is. nearly all newer (~96and up,gassers) that i have come across do this.

If you shim out the oil pressure relief valve you can get a little more oil pressure.

---------- Post added at 08:26 AM ---------- Previous post was at 01:08 AM ----------

This is why i did it.This could of happened for a number of reasons.I wanted to try a free fix.I have not looked at the rocker in a wile and i am not sure i want to.

Ouch... That got galled up...