Hey everybody. I think I'm having a little issue with my oil pressure. Before I purchased it, it was owned by my job and I bought it out of the auction. Our maintence schedural is one oil change a year or every 15,000 miles (full sythentic 5w-30). I recently did a cluster swap from an idiot light cluster to a qauge cluster. When the engine is cold my oil pressure is 40 to 45 psi. But when the motor and oil warms up it drops to 10 to 15psi at idle. Once I am driving or rev it up some it goes back up to 40psi pretty quickly. I am running full synthetic 5w-30 changed about every 5000 miles (I mainly do highway driving). Should I be worried or concerned about this oil pressure. The engine has about 175k miles and makes does make a very slight tapping noise but it has done this for the last 5 year I had it and it hasn't gotten any worse. Any input will be appreciated.

 

13# @ hot idle is minimum spec, some guys are running with quite a bit less without any troubles. You may want to address it at some point, but IMHO it isn't a pressing issue.
I'd get a mechanical gauge and verify the readings, you may find you have different numbers.

 

Your good. Synthetic usually runs a little lower,especially 5-30. With 175k miles you may want to step up to the next higher viscosity.
I run 15-40 on a tired engine and only show 4 to 5 psi at idle but it runs and runs.

 

What brand of oil filter is on there now?

 

This ^^^

And if this were mine, I'd change oil more frequently than 15k, even with full synthetic.

 

My 98 has 136xxx on it and i have the same thing going on. Really doesn't bother me because cold I have 45-50lb of pressure and hot I have 40 above 1500rpm but below I have like 10lb. I'd hook a quality mechanical gauge to it and get a reading. I dot know that I trust those sending unit deals on the side of the block

 

Look in valve cover through the oil fill cap. If you see oil moving around your good. Pressure at idle is meaningless. Flow is what is important,if there is oil up top that is a sign that oil is getting everywhere else. As long as pressure jumps up when above 1000 rpm I would not be too concerned.

 

Also a good way to assess how sludgy the engine may or may not be.

Still wondering what brand of oil filter is on there...........

 

I was thinking of putting a mechanical on there and checking it just to be be sure it is what the dash is saying.

I actually was going to try 15w40 I have some in my garage. Just haven't gotten around to changing it.

I have a wix filter on there. I believe the 51515 filter number. Its just a little longer then the stock filter which I think is a 51085 number (I could be wrong with this number).
I change it every 5k since 90% of my driving is highway. My job is the one that changes oil every 15k which I think is stupid.

Haven't done that yet I will have to look. And pressure does jump up once its off idle.

Since I had it every other oil change I have been doing 5qt 5w-30 1qt trans fluid to try and clean the motor up some since my job stretched its oil changes so far apart. And its a wix filter.

 

If you're on the synthetic bandwagon already Rotella T6 5W40 is some fantastic stuff.

Actually this is the ideal scenario for operating the engine with extended oil change intervals. In the owners manual 3k change interval is recommended for "severe duty" (city driving), highway is like 8k miles. 15k is a little silly in an old 4.0... that stuff is probably 5W20 when it comes out

 

Had the same symptoms on my 98. After about a year, oil started dripping out of the sensor housing down by the distributor. I replaced the sensor with OEM Chrysler. Before installing the new sensor, I ran a tie wrap down the hole the sensor screws into. Now the pressure is 55 cold idle, 50 hot at 2000 rpm, and 45 hot idle. Worst case on a really hot day, 35 hot idle. I have 203,000 miles on my Jeep.

 

THAT is a good idea. There's a whole thread about that on NAXJA or JF. I would never replace a sender without doing this again.

 

Whats a tie wrap?

 

aka zip tie. Thomas & Betts has a "Ty-Wrap" product

 

How does it help