So I recently changed my oil, put 6 quarts of penzoil high mileage in with some STP additive. I made sure to drain as much of the old oil as possible, turning over the engine after the drips died down to flush some of the channels out. I've noticed that my oil pressure is normal idling and stays around 40-60 on the road most of the time, but going up the slightest hill my pressure will raise up to 80+ until i let off the gas. The oil level is between "add" and "safe" but i have a feeling that theres too much. Either that or the STP is messing with the pressure. Any thoughts?

 

Not the best expert around here, but looks normal to me for these Jeeps.

 

6qt and stp is too much oil. only supposed to put in 5qt TOTAL.

 

Six. Capacity is six quarts.

That pressure is high, though. Makes me wonder if you don't have a defective filter.

 

The symptoms are of too much oil, but the dipstick shows otherwise. The filter is a fram x-guard or something like that, it wasn't cheap. I may try taking out a pint of oil and see how that affects things.

 

Yeah my bad, I always buy the big jug and a quart, so 6qts it is. Been a long time, since I thought of actual the oil capacity number. I just add fluid till it gets to the right point on the stick. STP will raise the pressure a little, by design. but it does sound like there is something else going on in the hill climb number being so high

 

I do same. Love those big jugs.

Bossokee, did you heat the motor up before draining the oil? It really sounds like you've got a partial obstruction somewhere.

 

The engine was over 120 degrees when i drained it, and i ran the engine for 1-2 seconds after it slowed down. The drained oil filled the empty 5 quart jug plus the old filter. It seems like there is too much oil but the dipstick shows otherwise

 

6qts is standard. i use 5qt jug + 1qt bottle

Some engines will also bypass after the oil clogs the filters to a certain degree; it could be the case that your pressure release valve is not working correctly, (Bad Oil Filter like nomeaculpa says) The pressure could possibly go up when this happens.

But, generally it is normal to have a (slightly) higher oil pressure after an oil change.
The viscosity of new oil is higher than that of worn out oil. As far as what is spec for your particular engine, I dont remember off the top of my head what it is for the 4.0L I6.

Last thing is; If you have enough moisture in the air, you can get some in the engine, but since its a fresh change, i doubt that you have water in there, and you would have noticed a milky white substance... Anyways, this can thicken the oil to the point to where there is more resistance in the engine causing higher oil pressure.

 

Id check the sender first, they are known to go bad.
Frams are known bad filters, the TG is a little better, but they still suck.

 

Somebody may well come along with a better idea, but I'd say run it for awhile. Heat it up good and see if it doesn't settle down.

Starting it without oil in it makes me nervous, even for a second or two. I'm thinking you may have loosened up some gunk that's caused a partial blockage. I'd just try to burn it out.

If it doesn't settle down pretty quickly, or starts overheating, I'd go for the kerosene.

 

Ive heated it up to operating temp quite a few times since the change which was a week or two ago. Could I have added too much STP? Its thick stuff but I only added 4-5oz worth i'd say.

 

It's funny that this happened to me too. I put new Castrol GTX and a new fram oil filter. I have a feeling this fram was making my pressure high because when it had a different filter the pressure was normal. If the problem occurs still try changing the oil filter to Bosch maybe.

 

Why are you running STP? I'm not particularly fond of it for modern engines. I used to use it back in the 70's though to "thicken" the oil up when I had an engine with marginal internal bearings, but only then.

Personally, I'd skip the additive. Oil has everything your engine needs. 6 quarts of quality oil. Use a GOOD filter. The lowest end orange Fram filter doesn't qualify there.

Then after the above, if you are in the below FACTORY SPEC range for oil pressure, you are fine:

*Not less than 13 psi at HOT idle

*Between 37-75 over 1600 rpms

When the oil pressure sending unit begins to fail, it usually fails HIGH, so that is still a possibility here. If you end up replacing it, buy it directly from Jeep for the best reliability/accuracy/mating with your factory gauge. It's worth the extra $20.

 

After I changed my oil filter adaptor o-rings and power washing the undercarriage my oil pressure gauge would occasionally show high numbers. I cleaned the sending unit's connector with electric contact cleaner then used dielectric grease (on the connector) and my oil gauge is back to normal (30-50 psi).