worleyburd

So I came across some threads of people talking about their oil pressure. Well I have a 92 5 speed 4.0 HO
And my pressure stays about 40 at idle. People are saying it should be 10. Is that right or has my jeep just been messed up since I got it haha.

samj

At idle mine's around 40, maybe a hair lower. When I get on the gas it goes up accordingly. '98 4.0L as well.

Demonoid369

13-40 ish is normal, most of the time as far as I've seen its usually at 40 or hair above or below. What size and type of oil filter can also effect the pressure also, when I was using jiffy's oil filter, it was usually under 40 a lot and wouldn't exactly keep a constant pressure, switched to napa gold(wic) and it now stays just a hair under 40 and stays like that unless I let go of the gas. Then it drops.
Also is it at 40 when its up to temp? Or higher?

samj

I've heard other people say the same thing as Demonoid said here. I currently have a Mobil 1 filter / oil combo still on from the PO and like I said earlier, have around 40 PSI at idle. I think it may have something to do with how dense the media in the filter itself is (not to say that more dense media filter = better), but Napa Gold/Platinum/Wix and Mobil 1 have very high quality filters. Jiffy Lube and Fram filters are little more than paper or recycled cardboard if you're lucky.

worleyburd

Well. It stays at 40 pretty much. Except when I haul *** ya know haha but yeah I don't think I've seen it go anywhere near ten, I've always used wix filters and 10-30. But my jeeps not acting up or anything i was just really thrown off by that. Seems crazy to me to have it go that low because it never has I guess

playbass

Anything above 13psi at hot idle is within spec.

Demonoid369

For the most part, 13-20 is where the pressure is for hot idle, and 20-40 is usually for cruising speed, its when your cruising pressure is at 13 then there should be some worry lol
Mine with a napa gold will be at 20 for idle and just a hair under 40 at cruising.
Can't remember the exact detail but I think its like 10psi for every 1k rpms? Don't quote me on that though lol its something like that. Who ever told you that cruising pressure is 13, you should warn them that there might be something wrong with their engine lol

salad

Yeah I've heard the 10k PSI thing as well. A healthy 4.0 seems to be above the middle of the gauge at cold idle, and below it when hot. Should build pressure under load. Your pressure is fine.

A big +1 to avoid cheapo filters. They have a habit if collapsing, and also don't really filter that well. In our engines a good filter is more important than the oil itself. Tons running 10w30 low end conventional with high mileage, no high milers with Orange Cans Of Death.

In my 4.0 the only time I've seen pressure around 20 PSI is after hauling *** on the freeway in 3rd gear (manual tranny). 4K RPM for 10 minutes or so really got him warmed up. Lol

RTorrez1

40 PSI at idle is perfect pressure. If you really have any concerns about it. You can always verify the pressure with a mechanical pressure gauge. I do have a feeling that you will be seeing a little lower pressure that you are seeing on the dash unless you don't have many miles on you engine or you recently had her rebuilt. It's always a good idea to verify you pressures and temps every so often since the dash gauges are known to be inaccurate many times.

bigbadon

Your OK. There are too many myths and misconceptions on pressure.
1. pressure is determined by how much internal leakage (clearances),wear,temperature,viscosity,RPM and mileage.
2. Pressure is not an engine function. It is an indicator of engine condition
3. If it is too low there is no simple way to correct it
4. Even if you could change the pressure any condition that caused it in the first place will still be there.
5. Unless you want to tear down the engine and investigate there is little you can do.
6. Quit worrying and drive it.
If it makes you feel better I have been driving for years with almost zero pressure at idle and 20 at cruise speed.

bruggz351

Mine is the opposite...
Cold it's off the dial. And my aftermarket gauge reads off the clock too @ 100 PSI..
Hot, it idles around 90+ and over idle it's back off the clock... cruising it fluctuates between 95 and off the clock..
So far, no issues.

cheers

Demonoid369

Something might be clogged? Kinda steep for pressure, I'd be worried

cruiser54

That's not right. Does this no matter what brand oil filter you use?

salad

You say aftermarket gauge, is that with a sensor or an oil tube? Something's wrong.

Sparkys92XJ

I have a 92 5 speed with a crate motor with about 25k miles and mine runs the same way. 40 at idle and I a ill higher when driving. I've seen it shoot up around 60 before. So there's nothing to worry about! Low pressure is what you want to keep your eye on.