Low oil pressure on high mileage motor (1 Viewer)

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May 1, 2017
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Portland, Oregon
I am looking for advice on a possible oil pressure issue.

We have 96 LC with almost 330k miles on the original motor. The vehicle drives great but we noticed recently the oil pressure seems lower then it has read in the past. The dip stick indicates the oil level is good. See pictures. I have included a picture of the manual for reference. The first picture of the oil pressure gauge is at idle.

We are planning to put on a mechanical gauge to verify the oil pressure. If low, it could be the oil pump but I have heard that isn’t a easy job to replace. Of course, it could be another issue. We recognize that the engine is high mileage and is likely showing it’s age.

As a side note, we are using a Castrol synthetic high mileage oil.

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Lots of threads on this- gauge is iffy. My observation is that most gauges (any kind) are only calibrated to their level of accuracy. Note there are no numbers on these. Most bled off through worn bearings. run heavier oil. Don't worry about it.
 
The sending unit could be going bad. The wire connection at the sender could be loose or corroded. Do not run a Napa/Wix brand oil filter as these have been defective and ruined more than a couple engines here on Mud. There is nothing wrong with running oil with a higher viscosity as mentioned above. My engine has 305k miles and runs like a champ. I’ve been running Delo 400 15/40 since I bought it at 265k. I suspect that you will discover ample oil pressure on the mechanical test gauge when you do that. The rule is, 10psi for every 1,000rpm. That means 7psi at idle is enough and 50psi at 5,000rpm.
 
Ignore it. Run a slightly higher viscosity oil if you like....but I can tell you as long as your engine isn't knocking you are fine.

I put a digital oil pressure gauge on mine (in conjunction with the factory unit) just to monitor it and regardless what your dash gauge reads (they are known to read low) you probably have 8-12 psi at idle. My engine has similar mileage and that is what I see.

Just be CERTAIN to always run a good quality oil filter (NO WIX) and check your oil 'level' often. Then put the oil 'pressure' out of your mind altogether.
 
I ignored it and than my motor went boom! Change out the sending unit and see if that helps at all. If it doesn't I would look into changing the oil pump.
 
Thanks for the advice! Makes sense. We’ll verify the psi via the mechanical gauge and try a slightly higher viscosity oil.
If the oil pressure is indeed low as indicated by a properly calibrated mechanical gauge, you might look into verifying the crank pulley bolt torque. Have you experienced any perceived weakness in the power steering?

Be aware that 20w50 is specified on other continents where our EPA hasn’t choked the people with its tentacles. I live just a bit NE of you and there has been no problem running 15w40 year around in my cruiser and my Cummins pick-up so 20w50 would probably work too. We don’t get extremely cold weather.
 
If the oil pressure is indeed low as indicated by a properly calibrated mechanical gauge, you might look into verifying the crank pulley bolt torque. Have you experienced any perceived weakness in the power steering?

Be aware that 20w50 is specified on other continents where our EPA hasn’t choked the people with its tentacles. I live just a bit NE of you and there has been no problem running 15w40 year around in my cruiser and my Cummins pick-up so 20w50 would probably work too. We don’t get extremely cold weather.

Didn’t think of that. Good point. I haven’t noticed any weakness in the power steering but will pay more attention to it.

We’ve been using 10w30 and agree that a heavier weight oil is worth trying. Thanks!!
 
I noticed a similar issue on mine today. 266k miles on the original engine. Oil pressure gauge sits where yours is at and at idle after the engine has warmed up the car rumbles pretty significantly. It doesn't do this at higher RPM. Following this.
 
Lots of threads on this- gauge is iffy. My observation is that most gauges (any kind) are only calibrated to their level of accuracy. Note there are no numbers on these. Most bled off through worn bearings. run heavier oil. Don't worry about it.
After oil changes, new filter, new sender unit, verifying wiring and gauge operation, listening to the engine, observing splashing inside the oil cap/spout, clearly seeing no leaks, and spending hours on IH8Mud with endless 'low oil pressure forums', I to will "Not worry about it". I'm done losing sleep over a fine working engine.
 

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