Oil Pressure Fluctuations?

[GLuttmer]

In my 98, 24-valve Dodge, the oil pressure gauge always stayed steady at a high-normal reading, regardless of RPMs or temperature. This seems to be true for many other 2nd generation Cummins owners that I’ve talked to.



On my new 03, 305 HO, however, the oil pressure gauge fluctuates between low normal and high normal, depending on temperature and RPMs.



QUESTION: Are other 03 owners noticing the same thing &/or is this something that I should be worrying about?



P. S. I did change out the original Mopar oil it came with after 6000 miles of mostly heavy pulling, but the new Valvoline Blue 2000 is acting much the same (although it doesn’t go as low as it used to, it does go a little higher).

 

[Mr.Goat]

Gluttmer



My 03 HO acts similar. When cold the oil presssure is at the high end of normal. As the engine warms up the pressure reduces to mid normal and pretty much stays put until you shut her down.

Can't say that I've noticed any pressure fluctuations with RPM's.

Pete

 

[Rosco]

I think what you are describing is a real oil pressure gauge that is doing it's job. From what I have read about 2nd gen trucks some of them had there oil pressure gauges "IDIOTIZED" to cure some low oil pressure readings that owners were complaining about. I have driven many dump trucks, flatbeds, and now firetrucks for a living and all of these had one of the "Big Three" (Detroit Diesel, Cummins, Caterpillar) under there hoods. In driving these I have noticed that diesels seem to have a lot more "range" in there oil pressure especially at hot idle when some have read near zero. So in my non proffesional opinion you have a real oil pressure gauge. Finally, for what it's worth both of the powerstroke rescue's that my F. D. uses seem to have "IDIOTIZED" gauges. These things never move from the middle/normal position no matter how cold or hot or how much throttle variation there is.

 

[Prairie Dog]

Mine does the same thing and I agree with Rosco. A real oil pressure gauge varies greatly with eng. speed.

So don't worry, be happy! (OK I'm sorry)

 

[Big MAK]

Yep; lot's of fluctuation; and the pros say it's normal. Freaked me out at first too; my 2nd gens didn't fluctuate nearly as much (more likely the gauge didn't fluctuate as much; to be more exact).

 

[jimnance]

Mine does the same. High normal when the oil is cold, mid-normal when warm at freeway speeds, and low normal at warm idle.



I question whether in fact it is the guage. The engine will have a pressure relief valve. This valves job is to assure that you don't overpressurize the system. If sufficient volume/pressure is always present then your pressures will stay near the value set by the pressure relief valve. It may be that older CTD's have more pumping volume, or perhaps the addition of the cooling nozzles for the pistons consume enough flow that the system cannot keep the pressure up to maximum values all the time. It is also possible that they have opened up some clearences for the same result.



Some years ago you would be alarmed if an old style small cam Cummins 855 motor wasn't showing 80 PSI while cruising. Later, Cummins changed the internals of the engine to a "high flow - low pressure" system. When they did that a warm cruise pressure of 45 PSI wasn't considered low.



My point here is that as long as the guage is within the normal range you shouldn't worry. The engine does not need as much pressure at idle anyway. Generally, you have way more pressure than the engine really needs. It's designed that way for safety.

 

[nickleinonen]

in the older 2 cycle detroit engines, their idle oil psi was 2-3 pounds. kinda low, but enough. them big locomotive engines range from less than 10 to 100+ pounds [40w is thick when @ -20°C]. a range can be good

 

[4xquadrod]

Mine works properly ( Fluctuating).



I use the 10 psi per 1000 rpms to keep my brain happy.



So at 3000 you should have at least 30psi ...

 

[CROW]

Mine does exactly the same thing, suspect that we are seeing the readings from a real gauge. Oil pressure is a little over 20 at idle and a little over 40 at highway speed when the motor is fully warmed up. Remember that this motor has 28 quarts of coolant and 12 quarts of oil. It takes a long time to warm all that up and thin the oil out. Have noticed on mine that even after the temperature gauge shows the coolant has warmed up that it still takes awhile for the oil pressure to drop down to what appears to be "normal" (e. g. 20 at idle). Appears as though it is taking longer for the oil to thin than it does for the coolant to warm up. I have noticed this on gas engines too.