Normal oil pressure

[kevin588127]

I currently have a 1500 with a 5.7. it is pretty much sewing machine quiet. My oil pressure runs 50-62 psi. I saw a video posted the other day on FB and noticed the posters oil pressure was 27 psi. Do they run that low? Main reason for asking is that there is a belief that low oil pressure is the cause of lifter failure on the hemis. Every 6.4 I've heard has had the lifter clatter.

 

[jetrinka]

Mine, hot idle in park is 34-35 and hot idle in drive sits at 30. Not low at all by any standard. I'd be more than happy with 27 too - the owner likely hasn't changed his oil in a while which can affect the viscosity level. If its sheared, diluted with fuel, etc.

I believe the lifter clatter you've been hearing, which is the most common noise, is just a resonance that seems to originate from the exhaust y-pipe area and nothing to worry about. An occasional cold start tick-tick-tick that goes away within a few seconds can be normal as well if the truck has sat for a period of time and the lifters have been allowed to bleed off or if the oil filter ADBV is defective or sucks. A cold start tick that doesn't go away or gets worse as the engine heats up is the true Hemi tick and while it is common isn't nearly as common as the internet would lead you to believe.

Hemi's also have a problem with exhaust manifold studs breaking which can manifest in a tick and goes away as the engine warms up. Not lifter related at all.

Just change your oil on time, use good oil and be happy.

 

[kevin588127]

Thanks for the reply. I have a 2500 on order. Test drove one with 27k on it and it was loud as hell the entire test drive. We also have a 3500 at work with 4k on it. It is loud but quiets down a bit when it warms. My current truck is somewhat of an anomaly. Many 5.7s don't have that high of oil pressure. I change oil every 5k and run Mopar or wix filters. Also had the pleasure of having the exhaust manifold bolts break.

 

[jetrinka]

I’d be questioning the integrity of the oil pressure sender or the gauge cluster if it’s reading that high of oil pressure at hot idle. Unless you are describing hot driving pressure. Mine hot while driving, depending on RPM will be anywhere from 54ish to low 60’s.

But if yours is reading that high at idle I’d be looking into it. What year truck? Mileage?

 

[kevin588127]

I've owned the truck since 3500 miles and it's always been that way. Cold start is 58, 62 is only seen while cruising and oil temp below operating temp. Hot idle is usually around 50 and cruising with oil at operating temp is mid 50s. The 5.7 runs a 5w20 so maybe that has something to do with it. I just thought 27psi seemed really low.

 

[OLEJOE]

My 22’ drops to 27 hot idling in gear. 51-52 hot at 70 mph but I’m getting close to an oil change at 5k miles.

 

[troverman]

The oil pressure gauge and / or the EVIC reading is entirely not accurate, from what I understand. It is simply a calculated algorithm the computer uses, to take the engine coolant temp reading, perhaps the ambient temp reading, and the engine RPM reading to generate a "predicted" oil pressure based upon everything working properly. The only real oil pressure reading is the simple pressure switch on the motor which reads "yes/no" depending upon pressure. Basically, if the oil pressure if above "X" psi, your red oil pressure warning stays off. If it is below that, it comes on. Fords are the same way. The older (mid 2000's) GM trucks had an actual oil pressure reading, not sure if they still do.

 

[jetrinka]

The oil pressure gauge and / or the EVIC reading is entirely not accurate, from what I understand. It is simply a calculated algorithm the computer uses, to take the engine coolant temp reading, perhaps the ambient temp reading, and the engine RPM reading to generate a "predicted" oil pressure based upon everything working properly. The only real oil pressure reading is the simple pressure switch on the motor which reads "yes/no" depending upon pressure. Basically, if the oil pressure if above "X" psi, your red oil pressure warning stays off. If it is below that, it comes on. Fords are the same way. The older (mid 2000's) GM trucks had an actual oil pressure reading, not sure if they still do.

Its an accurate reading. Many cars these days have actual oil pressure readings that if not able to be seen on the EVIC are able to be read in the data stream on scan tools and used as diagnostic data. This is assuming the sender is working properly which on a brand new truck I'd imagine is a moot point.

 

[Crusty old shellback]

5W20 is a thin oil. If it's at 50 PSI at warm idle, that's high.
Even when running a high volume oil pump on a built motor and 30w oil, I still only had 30 to 35 PSI at warm idle.

 

[troverman]

Its an accurate reading. Many cars these days have actual oil pressure readings that if not able to be seen on the EVIC are able to be read in the data stream on scan tools and used as diagnostic data. This is assuming the sender is working properly which on a brand new truck I'd imagine is a moot point.

Well, on a brand new Cummins truck, the oil pressure is a fake calculated value. I'm surprised its different on a gas truck. I guess I can hook up my scan tool and see if there is a PID for it...

 

[Crusty old shellback]

So I checked my oil pressure on the drive into work this morning.
'21 6.4 Hemi
3200 miles since last oil change.
5W-40 Castrol synthetic
Temp 203
Idle pressure 29-30 PSI
cruise at 35 MPH 54 PSI

 

[troverman]

I'll verify with my scan tool, but I don't believe there is a PID for oil pressure or oil temp. Those are just expected values calculated by the computer based upon a number of other real inputs, with the assumption everything is working properly. I'm betting when I hook up the scan tool, it will probably show a value of "OK" for oil pressure, meaning the pressure switch is a simple on-off function. There is also a known delta between coolant temp and oil temp that the computer can calculate for a given RPM and duration at RPM. The Cummins trucks show this same information and it is known to be calculated values only. I doubt the Hemi would have a real oil temp sensor and variable oil pressure sensor but the diesel would not.

So in other words, don't take too much stock in those readouts as they are basically fake.

 

[Crusty old shellback]

I have a scan tool but not sure if it will read my '21 as I bought it several years ago. I can try it and see what happens.

 

[troverman]

If it can show PIDs, it will show everything that is there. I believe @Jimmy07 can confirm there are no PIDs for these readings.

 

[Jimmy07]

I'll verify with my scan tool, but I don't believe there is a PID for oil pressure or oil temp. Those are just expected values calculated by the computer based upon a number of other real inputs, with the assumption everything is working properly. I'm betting when I hook up the scan tool, it will probably show a value of "OK" for oil pressure, meaning the pressure switch is a simple on-off function. There is also a known delta between coolant temp and oil temp that the computer can calculate for a given RPM and duration at RPM. The Cummins trucks show this same information and it is known to be calculated values only. I doubt the Hemi would have a real oil temp sensor and variable oil pressure sensor but the diesel would not.

So in other words, don't take too much stock in those readouts as they are basically fake.

Unlike the CTD, the 6.4 Hemi does have oil pressure and temperature sensors.

 

[troverman]

Thanks Jimmy, good to know. I stand corrected!

 

[filicili]

Hey guys i have kind of a different problem. Me and my father are buying a 5,7 Hemi and when we test drove it the pressure only went to like 36 hot in drive from the 30 on idle. So im asking what could be wrong with the car?

 

[kevin588127]

Hey guys i have kind of a different problem. Me and my father are buying a 5,7 Hemi and when we test drove it the pressure only went to like 36 hot in drive from the 30 on idle. So im asking what could be wrong with the car?

According to some, there is nothing wrong with the truck. Different filters and oils will result in different oil pressures. That's a bit low for my liking on a 5.7 as mine always ran 50-60 psi. I always ran a quality filter and quality oil that met the Chrysler spec. My current 6.4 has 3k miles and pressures are lower than they were on my 5.7.

 

[filicili]

According to some, there is nothing wrong with the truck. Different filters and oils will result in different oil pressures. That's a bit low for my liking on a 5.7 as mine always ran 50-60 psi. I always ran a quality filter and quality oil that met the Chrysler spec. My current 6.4 has 3k miles and pressures are lower than they were on my 5.7.

Ok thank you so much.