4.0L I6 Jeep

[wsar10]

Originally Posted By: MrRPM
60 PSI of oil pressure in a 4.0L jeep? seems kinda high if thats at full temp

again that lucas is thickening up your oil way more then is needed.


the 4.0 should be 13psi at idle, and should range 37-75psi above 1600rpm.

 

[southernjeeper]

no lucas for the 2days the T5 has been in it. It did I ADMIT seem smoother coasting while driving. Not cruising, but coasting. The tapping of the valves after I got in this evening seemed just as good if not better than when I was running the Valvoline's Maxlife oil. So I'll just see after a few weeks how my mileage differs as well.

The reasoning behind the oil pressure is due to the fact when I replaced the rear main last year. I had the oil pump replaced with a new one. So wouldn't that cause the pressure to be better? And wouldn't a higher psi be better because everything is getting oil where it needs to be in the engine? What about better compression with the new oil pump?

I'll check tomorrow when I drive perhaps a 7mile stretch on the interstate and see what the oil pressure does once I get to a stop then and let it idle for a minute or two.

.

 

[rslifkin]

Most 4.0s I've seen run around 35 - 40psi oil pressure at hot idle (with around 100k miles on them), and 50 - 55 at higher rpms.

 

[MrRPM]

with my jeep at FULL temperature running Mobil 1 TDT 5w-40 and a P1 filter I will idle at 38 PSI and run anywhere from 42-52 PSI with rpm.

55-60 psi if its cold out and the oil is cold and im running it at a higher RPM

 

[ltslimjim]

Originally Posted By: southernjeeper
no lucas for the 2days the T5 has been in it. It did I ADMIT seem smoother coasting while driving. Not cruising, but coasting. The tapping of the valves after I got in this evening seemed just as good if not better than when I was running the Valvoline's Maxlife oil. So I'll just see after a few weeks how my mileage differs as well.

The reasoning behind the oil pressure is due to the fact when I replaced the rear main last year. I had the oil pump replaced with a new one. So wouldn't that cause the pressure to be better? And wouldn't a higher psi be better because everything is getting oil where it needs to be in the engine? What about better compression with the new oil pump?

I'll check tomorrow when I drive perhaps a 7mile stretch on the interstate and see what the oil pressure does once I get to a stop then and let it idle for a minute or two.

.


Extremely low oil pressure and too-high oil pressure are both bad things.

An oil pump positively displaced the fluid as the ENGINE is the source of the pressure. The amount of pressure being too high is a result of running too thick. One must find an actual gauge, compare to values specified for full temp and startt-up. Also, there is 'oil pump relief' mode to consider so there is a designed 'reading' of a pressure drop depending on the conditions and the way the vehicle is being driven.

I'd suggest finding the typical hot-idle 'pressure' readings and go from there.

I'm not experienced enough in this area, but that's a gist anyway.

 

[southernjeeper]

It's doing what it has in the maintenance manual now. It would not however with the lucas oil stab. and the Maxlife 10w30. Which would keep the pressure high...

I did notice today that it fluctuated and did get below the 40psi mark after about 20minutes of driving. The one thing I think I lost by not using the lucas is my passing/pick up capability. I was better at getting up to speed with the stuff that y'all hate???!! SO I like the get up and go that my jeep had while I was using the Lucas. The torque a little jeep has is great!


Itslimjim -- that makes perfect sense. Thanks for putting in your 2cents worth good ole honest truth about the subject.

 

[southernjeeper]

Originally Posted By: MrRPM
60 PSI of oil pressure in a 4.0L jeep? seems kinda high if thats at full temp

again that lucas is thickening up your oil way more then is needed.





MMM I was curious to the T5. Now I think I am curious to what the tacoma we have that has 120,000miles would act with the T5.

I have to say that BITOG was a very good (great) forum board to find since topics are about all things mechanical and what not. Kudos to Bob.

 

[wsar10]

Originally Posted By: MrRPM
60 PSI of oil pressure in a 4.0L jeep? seems kinda high if thats at full temp

again that lucas is thickening up your oil way more then is needed.



I quoted those numbers from the Factory Service Manuel (not to be confused with an owners Manuel.

oil PSI an jeeps are strange, and always seem kinda high I've owned quite a few jeeps.

 

[MrRPM]

very interesting, sounds like just as long as your at or above the 10PSI/1k RPM rule and not above 70PSI then Jeep is happy.

But remember to some people that in 2002 maybe 03 in the jeep wranglers anyway they started using dummy gauges for oil pressure.

if IIRC they did it even earlier in grand Cherokees with 4.0Ls

 

[wsar10]

Originally Posted By: MrRPM
very interesting, sounds like just as long as your at or above the 10PSI/1k RPM rule and not above 70PSI then Jeep is happy.

But remember to some people that in 2002 maybe 03 in the jeep wranglers anyway they started using dummy gauges for oil pressure.

if IIRC they did it even earlier in grand Cherokees with 4.0Ls


yeah my WJ has a tard guage, my ZJ has a real guage.

 

[84zmyfavorite]

Base model Cherokees, Wranglers and Grands have had the option of oil pressure gauge or Idiot light since they were first introduced(1984 Cherokee, 1987 Wrangler, 1993 Grand). 13 P.S.I. is the LOWEST allowable oil pressure in a 4.0. NOT what it SHOULD be from the factory or early in its life.

 

[jeepman3071]

Originally Posted By: 84zmyfavorite
Base model Cherokees, Wranglers and Grands have had the option of oil pressure gauge or Idiot light since they were first introduced(1984 Cherokee, 1987 Wrangler, 1993 Grand). 13 P.S.I. is the LOWEST allowable oil pressure in a 4.0. NOT what it SHOULD be from the factory or early in its life.


x2, 13 PSI is the lowest acceptable pressure according to the factory service manual. If I run 5w30 in the summer my Jeep with over 100k miles has 15 at a hot idle on a 100 degree day. Running a HDEO I have 22-25 psi hot idle. With that said I've seen 4.0L's that have over 250k miles with a little under 10 psi hot idle, and they run quieter than mine does.

 

[rslifkin]

03 and 04 WJs have fake OP gauges. The 02 and older have real gauges.

 

[jdoria]

I just changed out the Rotella 15w40 and Wix filter after 300 miles and added Pennzoil Platinum 10w30 and a Bosch Distance Plus filter. The Rotella was still gold coming out of the engine.

It is a Night and Day difference from the Rotella. 15w40 was not the right oil for this engine. I felt that from the second I started the engine with the Rotella in it.

With the Pennzoil, I noticed an instant difference in idle, oil pressure, engine sound, and drivability.

I'm going to leave the Pennzoil in there until January. I dont think I'll have driven this car an additional 1,000 miles by that time. I figure why not change it anyway, it may be cleaning something out as it advertises.

 

[wsar10]

Originally Posted By: jdoria
I just changed out the Rotella 15w40 and Wix filter after 300 miles and added Pennzoil Platinum 10w30 and a Bosch Distance Plus filter. The Rotella was still gold coming out of the engine.

It is a Night and Day difference from the Rotella. 15w40 was not the right oil for this engine. I felt that from the second I started the engine with the Rotella in it.

With the Pennzoil, I noticed an instant difference in idle, oil pressure, engine sound, and drivability.

I'm going to leave the Pennzoil in there until January. I dont think I'll have driven this car an additional 1,000 miles by that time. I figure why not change it anyway, it may be cleaning something out as it advertises.




it's usually used in older 4.0's w high miles AFAIK.

I run the Rotella T5 in 10-30 and it works nice, I love it.

 

[KCJeep]

My "newer" 04 WJ did not take a liking to 15w40 either, although at first I thought it was fine after about 1000 miles it was clear my 4.0 didn't like it. I had to drain some and add a quart of MMO and now it's fine. Back to 10w30's which have always done well for me in the 4.0, I like Rotella anyway which is the easiest HDEO to find in 10w30.

Like wsar10 mentioned, many guys have run 15w40 without issue in the 4.0, which led me to try it as well, but he astutely observed most of those were in "older" 4.0's.

 

[jeepman3071]

15w40 is a bit heavy for the 4.0L in my opinion. I've run 5w40 Rotella T synthetic with good results but a 15w40 will definitely give you some start up noise in colder climates. Rotella T5 10w30 seems to be a good oil for the 4.0.

 

[MrRPM]

I went from Valvoline Durablend in my jeep noticing alot of noise from the engine when accelerating at low speeds with the top off
to mobil 1 TDT and all that noise is gone under the same conditions.

these engines may be strong and not care alot about what oil it has, but they do seem kind of picky about the oil if you listen carefully and analyze closely.
so far the 5w-40 works great for me but we will see what Michigans cold winters brings

 

[southernjeeper]

Originally Posted By: MrRPM


these engines may be strong and not care alot about what oil it has, but they do seem kind of picky about the oil if you listen carefully and analyze closely.


well said. They are just picky eaters. What brand of gas and which oil they like is all part of the fun. Especially with our good ole jeeps.

 

[84zmyfavorite]

Its my belief that Good condition, Tight clearance 4.0s do run better with a 10w-30, or even a 5w-30 in cooler temps. Ive had a handfull of these 4.0s in my time, two of which I still have now, one of which is my 99 with its Freshly Built 4.0 that Im driving today, the other being my Beloved 2001 SilverStone Metallic Jeep Cherokee with its 64,606 mile 4.0. Neither of these Good, Tight engines "Mind" thicker oil(Custom Break-In Oil for the 99 was somewhere in the low Straight 30s), and I have put 15w-40 Diesel oil in my 01, with Good results actually. My 01 has Quaker State 10w-40 in it right now. I do believe that High Mileage, Severe useage 4.0s DO like heavier weight oils like Straight 30s, Diesel 15w-40s, and even 20w-50 weight oils to "Fill" in the gaps between Worn moving parts. Those Newer, Tight tolerance engines discussed before might make noise with thicker oils because they are not getting suffecient oil to their Tight Tolerance moving parts. Thats my humble opinion, Im only right about half the time anyways. I use 10w-30 or 10w-40 in Good Jeeps with 4.0s, and Straight 30 usually in Worn Jeeps.