Idle Oil Pressure Difference

[mbridge1]

I've roughly 16K miles on my 2021 Ram. Since I first bought it until about a month or so ago the oil pressure at idle was ~22 PSI. About a month ago I noticed the oil pressure at idle was now hovering around 31 PSI. I was coming due for a 5K mile oil change, and chocked it up to possible break down in the oil, but I'd take note of it once I had fresh oil in the engine. Got the oil changed at the dealer today, and the idle oil pressure remains around 31 PSI. Oil weight is 5w-20 full synthetic. Has anyone else seen the same thing? Not overly concerned about it, just noticed something different.

 

[Aseras]

If the oil was breaking down, it would usually get thinner first, then thicken and be sludge. The oil psi reading in the cluster is a "fake" computed value based on RPM and temperature. There's no real pressure sensor other than a low oil pressure idiot switch that lights the oil CEL red light, not the low oil pressure ( < 10 psi calculated ) DIC message.

 

[Bassinb]

Mine hangs around 35-40 at idle

 

[SD Rebel]

Once warmed up, maybe after 10 minutes of driving, sitting at idle I usually see 29F - 31F. The oil needs to be at least 200F for me to see that low a pressure.

Even on the hottest day, sitting at a long idle, I never see the pressure below 29F.

 

[SD Rebel]

If the oil was breaking down, it would usually get thinner first, then thicken and be sludge. The oil psi reading in the cluster is a "fake" computed value based on RPM and temperature. There's no real pressure sensor other than a low oil pressure idiot switch that lights the oil CEL red light, not the low oil pressure ( < 10 psi calculated ) DIC message.

That's interesting, so the digital oil pressure is based of a computation of rpm and temp? You confirmed that is the case for these DT Rams, because they do sell oil pressure sensors for the DT Rams, though I'm assuming that's the low oil pressure sensor you mentioned?

 

[Aseras]

That's interesting, so the digital oil pressure is based of a computation of rpm and temp? You confirmed that is the case for these DT Rams, because they do sell oil pressure sensors for the DT Rams, though I'm assuming that's the low oil pressure sensor you mentioned?

Yep, there's some threads on it here somewhere. I think in the tuning thread. One of the popular mods it to put a real oil pressure sensor in. The stock dead switch trips at 8psi. Thats the red oil can light, not the message. It does have some other values, like the oil pump resistance and a few other things. Its supposedly pretty close, if the engine is working properly. If there's actually a problem, you can't trust it though as it makes a lot of assumptions.

There's also a couple of TSB's for some trucks to reprogram the ECU, the formula as sometimes it reads very wrong ( absurdly high or low ) on some trucks due to sensor/part changes.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10188793-9999.pdf

that the one I can find.

 

[SD Rebel]

Yep, there's some threads on it here somewhere. I think in the tuning thread. One of the popular mods it to put a real oil pressure sensor in. The stock dead switch trips at 8psi. Thats the red oil can light, not the message. It does have some other values, like the oil pump resistance and a few other things. Its supposedly pretty close, if the engine is working properly. If there's actually a problem, you can't trust it though as it makes a lot of assumptions.

There's also a couple of TSB's for some trucks to reprogram the ECU, the formula as sometimes it reads very wrong ( absurdly high or low ) on some trucks due to sensor/part changes.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10188793-9999.pdf

that the one I can find.

That's awesome info, thanks for posting!

 

[Cbty2050]

Yep, there's some threads on it here somewhere. I think in the tuning thread. One of the popular mods it to put a real oil pressure sensor in. The stock dead switch trips at 8psi. Thats the red oil can light, not the message. It does have some other values, like the oil pump resistance and a few other things. Its supposedly pretty close, if the engine is working properly. If there's actually a problem, you can't trust it though as it makes a lot of assumptions.

There's also a couple of TSB's for some trucks to reprogram the ECU, the formula as sometimes it reads very wrong ( absurdly high or low ) on some trucks due to sensor/part changes.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10188793-9999.pdf

that the one I can find.

That TSB is for a 3.0 eco diesel.

Oil pressure sensor is a direct input to the PCM. It is calculated off the resistance change in the sensor due to pressure change.

 

[stevj]

For the 5.7L engine, the oil pressure sensor is located on the right front of the engine, and measures pressure of the output of the oil filter.
As Cbty2050 stated, the sensor feeds the signal to the PCM and, as with so many vehicles these days, the PCM sets the cluster pressure readout or gauge needle.

Steve