Oil Pressure Question

I have a 97 4.0 4wd with 26,000 on a brand new engine from jeep. the question is when i'm driving the oil pressure will be 40 psi but then when i'm sitting at an idle it will drop down to 10-20 psi, it's done this ever since i got the jeep back from the dealer, I'm trying to sell it and this is the only thing the buyer is concerned with thanks alot

Chris

13 at an idle is the factory spec.

This is normal for a 4.0

13psi is within spec at a hot idle.

As long as it jumps right up to 30-40 when you're cruising, it's fine.

GREAT, that's good news guys, thanks for the replies so fast

Chris

What Viscosity of Oil are you using? That will effect oil pressure significantly. But if your getting factory spec oil pressures, it sounds like you've got the right Viscosity.

If too many nervous buyers are being scared off by 10-20 PSI at idle, even if it is factory spec, going up a grade in viscosity might raise that oil pressure.

yeah, you could run 10w40 and get better pressure.

Warm idle and hot idle are two very different things, I also was getting as low as 10 at hot ilde (the manual said 14 was as low as it should get at hot idle), so I ran a quart of lucas oil and it brought me up to 15 at hot idle, and probably 50 crusing on the highway, much better.

Read this thread for a good discussion on it: http://www.naxja.org/forum/showthread.php?t=911029

There is even 15W40 and 20W50 that will bring up that pressure even more, but my philosophy is too use what is recommended and measure its effectiveness by the oil pressure. If oil pressure is factory spec, then it should be working like designed.

Although, I personally would also be worried if idle oil pressure was just 10PSI, I would probably use a thicker oil, even if the book said it was OK.

BTW, more than spec oil pressure, especially when cold, can be bad, it may mean the oil is NOT circulating as fast as its supposed too.

I only suggest upping the oil viscosity to convince a doubtful buyer that doesn't want to believe the factory spec is true.

cguthrie said:

I have a 97 4.0 4wd with 26,000 on a brand new engine from jeep. the question is when i'm driving the oil pressure will be 40 psi but then when i'm sitting at an idle it will drop down to 10-20 psi, it's done this ever since i got the jeep back from the dealer, I'm trying to sell it and this is the only thing the buyer is concerned with thanks alot

Chris

Click to expand...

Just A bit curious, what was the dealer doing to the jeep?

Was it Jeep (new) dealer, or used car lot?

26,000 miles is real low for a 97 model, sounds suspicious. How long (yrs & miles) have you had the jeep? Why are you selling it?

Most jeeps here with that few miles are still getting 30 psi at hot idle with 10W30. This is first I heard of having low (10-20 psi) idle pressure at those few miles.

Anyone else have less than 20-25 psi hot idle pressure with 10W30 and less than 50,000 miles on a new jeep?