1998 Jeep Cherokee (XJ) Oil Suggestions

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Hey guys!

Thanks again for the help on my '98 Ram thread, now I have another question.

I have a 1998 Jeep Cherokee- 4x4

4.0L Automatic - 143,000.

Driven about 50-120 miles a day, about 70/30 Highway City.

Bought the Jeep at 130k, replaced the floors, and did some small engine /suspension work. It seemed to be pretty neglected, and had some decent lifter noise on startup, went away after my first oil change with it.

Been running Mobil 1 10-30 High Mileage with a MOPAR filter for about 4-5k OCI's just because I didn't know the history of the engine.

Does not burn any oil, maybe get a drip or two from the rear main not enough to be noticeable.

Looking for a suggestion/opinion on a lower viscosity oil? Different filter? Would like to stay synthetic, price isn't an issue.

Thanks again fellas!

Here's a picture of it.

 
Saweeett looking XJ bud!
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These engines are spec'd for 10w30 and for good reason, so stay with that over a lower viscosity such as 5w30. It's not so much the operating characteristics as shear is the reason, the 4.0 does not like anything less than a good 30 grade and when the 5w30 inevitably shears it is too thin for optimum protection in the venerable 4.0.

Mobil 1 has consistently produced up to 4 times more iron in UOA's in this engine than just about any other oil, but the best Mobil 1 UOA's have been with the HM version you are using. So I'd suggest you find a new synthetic 10w30, but if you're stuck on Mobil stay with the High Mileage.
 
That XJ is worn out and beat up - you should just donate it to me
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haha - Nice looking Cherokee!

The 4.0s aren't picky about oil. Any 5w-30, 10w-30 or 5/10w-40 will work perfect.

I'm a fan of the larger Fl-1A ford filter in the Cherokee 4.0.

I have been running RT6 5w-40 in mine, last oil change was on a 5w-20/5w-30 blend .... I'm going back to RT6 as I'm due for an oil change.
 
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Originally Posted By: Miller88
I have been running RT6 5w-40 in mine, last oil change was on a 5w-20/5w-30 blend .... I'm going back to RT6 as I'm due for an oil change.


I did a run of 5w20/5w30 blend in mine also, then did a UOA and it was NOT good.
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Too thin IMO. Stay with that T6!
 
Interesting guys thanks,

Now maybe im nuts but I had an FL1A in my garage from an '86 Crown Vic and could not get it to thread on! Am i just an idiot??

That T6 has me interested 5W-40? Will I have to be worried about shearing issues as mentioned by KCJeep? or is that solved by not being a 5W-30 but a 40?

Thanks!
 
Originally Posted By: George1992
That T6 has me interested 5W-40? Will I have to be worried about shearing issues as mentioned by KCJeep? or is that solved by not being a 5W-30 but a 40?


Bingo! It will still likely shear, but down to a "thick 30" at most. A 5w30 can shear down into 20 grade range, not a good match for the 4.0. The 4.0 needs at least a solid 30 grade, but will tolerate much thicker oils without apparent issue.

My buddy is running T6 in his XJ as well and really likes it.
 
I think T6 it shall be for the next OC.

Going to do a UOA for this current M1 run (it'll be 6k) just for the heck of it, then the same for the next with T6.

Now provided nothing major shows up in this UOA, 6k with the T6 and a Mopar filter should be ok correct?

Thanks!

George
 
Yep. The T6 may be good for closer to 10k but I wouldn't push it that far with a UOA.

A Motorcraft is identical to a Mopar except for the paint and the price. Both made by Purolator. You can't get the "spec" size in a Motorcraft any more, but many guys run the original larger size for that engine which is the very common Motorcraft FL-1A.

Nothing wrong with running the M0-090 either, it does say "Jeep" on it!
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I look forward to your results. I'm still on the bulk Valvoline 10W-30 that was in the car when I bought it, and am having trouble picking what I'll use next.

You mention the car was neglected, but you must have done a great spit shine job, Jeep looks great!
 
over on jeepforum the most popular oils for the 4.0 are QS Defy and Rotella T5 neither is a full syn but both common recommendations
 
Nice XJ!

Both me and KCJeep have found that our 4.0s run quietest with Pennzoil Yellow Bottle due to the high moly content. I think Pennzoil Yellow bottle 10w30 would be perfect for the 5,000 interval with the Mopar filter, and you'd save a bit more over the synthetic.

I ran Mobil 1 HM 10w30 in my Jeep, and it burned a whole quart in 3,000 miles. It had never consumed oil before that, and once switching to another oil the consumption stopped.

I think for the price, you can't go wrong with Pennzoil Yellow bottle 10w30 or the Rotella T5 10w30. Both are a great oil for the money.
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My jeep had a slight rear main seal leak the 4.0s are known for, nothing left on the ground in the morning but if you touched the area your hand would be wet with oil. After 3 OCIs (early on my 3rd now) of Quaker State DEFY mileage starting at 84k and now at 91k, the Rear main seal is dry to the touch. I haven't run a UOA yet with defy but I wanted to do a few short OCIs with the defy first anyway.
so Far I'm very happy, runs quieter then the fill of m1 0w-40 I used before but really its hard to compare that kind of thing anyway.
 
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I've run Defy once so far and liked it, Jarlaxle did a Jeep 4.0 UOA on Defy as well and it looked really good.
 
Originally Posted By: Troy_Hale
You mention the car was neglected, but you must have done a great spit shine job, Jeep looks great!


It took some time with a buffer to get that paint to shine again! Thank you! The body work wasn't fun either but it's nice knowing I'll never have an issue with the floors again.

I think I'm gonna go with the T6 just because I really prefer a synthetic, no hate towards Pennzoil, it's obviously a great oil, but just rather have a synthetic in there. Still want to try Platinum in my brothers T-Bird someday.

I will be sure to post the UOA results from the 6k run on M1, @ 142,500 right now, changing at 146 so should be by late june early july at the latest. (I drive a lot haha!)


George
 
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