> Main > Diesel Index > FAQ > Oil Pressure
Ram Oil Pressure Questions
Visit Geno's Garage
for Truck accessories.
Geno's Garage Truck Accessories

Q: My oil pressure has always been 35psi at idle when warm.  After the last oil change, my oil pressure was been hovering around 40psi. Would this indicate a low or high flowing filter? Or maybe a batch of ~30W-40 rather than 15W-40 oil?

It's not unusual at all to see idle oil pressure go up after an oil change. The oil pressure regulator is before the oil filter, so the oil pressure is "set" before the oil goes through the filter (with its pressure drop). New filters typically have less restriction than used filters, so having more oil pressure after a change is not unexpected. The oil pressure gauge is in the oil rifle after the oil filter, so you do see the "system" pressure on the gauge.  

Q: The oil pressure will always sit at that same spot above ~1500 rpm whether hot (500 miles at 100 degrees) or cold. Does this mean that a "high pressure" valve is limiting pressure?

As far as the "cruise" oil pressure staying at ~60 psi, we've found that the oil pressure gauge on '98 and later Dodges with the "Smart Cluster" dashes is not totally linear. Even if the oil pressure increases a fair amount above the 60 psi reading, the gauge doesn't move much, so not seeing much.

Q: The oil pressure on my 98 ISB will occasionally drop to 0 psi when I stop for a traffic light in hot weather. The warning buzzer and engine warning lamps also illuminate. My dealer has been unable to find a problem. Should I take it to Cummins?

You might want to have the oil pressure tested for peace of mind.   There is an oil gauge anomaly on the Ram ISB where the pressure drops slightly at idle, but the Ram PCM fails to properly communicate with the Cummins Engine Computer, so the Dodge PCM indicates no pressure even though there is no problem. Josh B. posted a note about this, but it is lost in my mail somewhere and I will post it as soon as I can locate it. TSB 08-22-99 was issued to correct this problem.

Q: Where does the oil go, back into the pan??

In 12-valve B-Series engines, the oil being "dumped" out of the pressure regulator goes back to the pan. In 24-Valve ISBs, the "dumped" oil is recirculated back to the inlet of the oil pump.           -Josh B.



Last Update: May 3, 2001