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99 XJ 108k miles 18psi oil pressure at idle, 40-50psi while driving

Oil viscosity?

Brand oil filter?

Checked that pressure with a mechanical gauge?

Inquiring minds want to know.
 
For peace of mind I like to remember that most idiot lights don't even kick on until it gets down to5 or 6 psi. Makes me feel good about my 15psi @ idle.
 
That is where mine is too, but Joe is right if you want a better answer more info and a mechanical guage reading. Gotta love his logic even when it hurts.
 
sounds good to me
 
You can rent a mechanical oil pressure gauge for a few bucks at many parts store.

Unscrew the oil pressure sending unit, install the gauge with the proper adapter, then compare what you get with the mechanical gauge to your dash gauge reading.

That way you'll know for sure, as it is possible there is some inaccuracy between the oil pressure sending unit and the gauge.

But even if it is 18 psi at hot idle, that is still okay and you shouldn't worry.
 
That's about where my 99 runs except when it's got fresh oil and filter. If you're using a generic filter, you might get it up a wee bit by switching to a premium Wix or Bosch. For some reason my 99 has run a bit lower pressure than its predecessors, but it hasn't changed in the 100+ thousand miles I've had it (now at ~254k), so I have stopped worrying about it. It's at the low end of the normal range, but normal range is good enough.
 
My 91, 96, and 98 idle at around 20 (ballpark) and run at around 35-45 normal driving when hot, so I think you're fine.
 
If you feel uncomfortable about it, replace the conrod bearings next time you have the pan off. That will raise it for 10's of thousands of miles. Worked on my 90.
 
Here are my readings after running for 30 minutes and 50 degrees Fahrenheit outside temperature. Sometimes it gets as low as 35psi when I run it longer.

1127001223.jpg
1127001224a.jpg
 
18 is not low. It is in spec.

Verify it if you want with a mechanical gauge, but worrying about a number that is in spec. or digging into the motor is absolutely not necessary.
 
i have a 98 with 367,ooo+ and it runs 45-50 whem cruizing and around 19 or so at idle....MY DD...lol
 
90Pioneer said:
I know the factory minimum is 13 psi at idle for 4.0 engines but doesn't 18psi seem a touch low?
Click to expand...

This cracks me up!!!!!!! Ever wonder why they call it a MINIMUM spec? Last time I looked, 18 was higher than 13.

You answered your own question, AND admitted to knowing the answer to your own question all in your original post. Plus, I'm sure there are other threads on this issue, in fact, I know there are, I've seen them!

Try using this logic next time you get pulled over for speeding...."officer, I know the speed limit is 55, but doesn't 70 seem a bit slow??" See what happens.....
 
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