What oil do you guys use on your 4.0s?

[Kenneth G Zinis]

In PA see temps all over the map. POs used to use Mobil 1, so I used syns for a while. Had a little weeping from rear main seal. Started using conventional 10-30, rear seal is now dry and Wrangler tap is only intermittent. If you can get high Zn oil like Valvoline VR oils.

 

[Jerry Bransford]

In PA see temps all over the map. POs used to use Mobil 1, so I used syns for a while. Had a little weeping from rear main seal. Started using conventional 10-30, rear seal is now dry and Wrangler tap is only intermittent. If you can get high Zn oil like Valvoline VR oils.

Good decision on the conventional 10W-30, that can save the seals from starting to leak But on a stock TJ engine I would NOT waste my $$$ or time adding more zinc to what's already in the engine oil. Yes the industry was forced to reduce how much zinc is present to prevent damaging the catalytic converter but it's not so low that it causes engine damage to a stock TJ engine. There's not even pressure on the cam lobes from the factory valve springs to cause damage as evidenced by the severe lack of complaints of valvetrain damage in our TJ engines. If I was running a high-performance race engine with a high lift cam and stiffer valve springs I'd definitely be adding additional zinc but I'm not so I don't.

 

[Pantera99]

Good decision on the conventional 10W-30, that can save the seals from starting to leak But on a stock TJ engine I would NOT waste my $$$ or time adding more zinc to what's already in the engine oil. Yes the industry was forced to reduce how much zinc is present to prevent damaging the catalytic converter but it's not so low that it causes engine damage to a stock TJ engine. There's not even pressure on the cam lobes from the factory valve springs to cause damage as evidenced by the severe lack of complaints of valvetrain damage in our TJ engines. If I was running a high-performance race engine with a high lift cam and stiffer valve springs I'd definitely be adding additional zinc but I'm not so I don't.

Hmmm, I usually run Valvoline Maxlife & seems to have helped the rear main leak. Was gonna try Castrol HM but I see its semi synthetic too. Maybe I'll just try regular conventional. Was thinking of checking the valve pan cover bolts too because there's alot of gunk towards the back of the valve pan.

 

[Rickwhoo]

What's everyone's opinion on using "High Mileage" Mobile One in their 4.0's? Does it do anything?? My TJ has 178,000 miles on it.

 

[Ashim]

What's everyone's opinion on using "High Mileage" Mobile One in their 4.0's? Does it do anything?? My TJ has 178,000 miles on it.

I believe it will help reduce any seal leakage. My 2004 has always had some rear main seal leakage since I bought it in 2007 at 31K miles. Originally I ran Valvoline 10W30 and did oil changes at 3000 miles. Later I switched to Mobil One EP synthetic 10W30 and 5000 mile oil change intervals. Several years ago I switched to Valvoline semi-syn high mileage 5W30 and noticed that my rear seal leak is much less, almost negligible. I'm changing once a year now since my miles are down. Didn't quite make 4000 miles this year. Now at 146K miles.

 

[Peppergat]

What's everyone's opinion on using "High Mileage" Mobile One in their 4.0's? Does it do anything?? My TJ has 178,000 miles on it.

I tried Orielly house brand high mileage conventional oil the last 2 oil changes and it definitely slowed my rear main leak down to nearly nothing. I change mine every 3K and it’s still really clean when I change it.
I did go back and forth on trying a full synthetic but have not tried it.

 

[John Cooper]

I use the Havolin 6 quart box from Walmart. 10W30 high mileage.

 

[Link]

The key is the high mileage rating. NOT the synthetic vs non-synthetic. Most of my vehicles I change the oil between 6k miles and 10k miles. Since I run my Jeep off road in dusty conditions, I like to change the oil more frequently. I usually change the oil and filter between 3-4k. It's probably excessive but I'm ok with it. Oil is cheap and engines are expensive. I use Super Tech 5W30 High Mileage synthetic oil. I like it. I had a few drips from the rear main seal before switching to the above oil. Once I switched, after a few hundred mile drive it stopped leaking. Hasn't been leaking since.

 

[Weasellee]

Penzoil 10w30 High Mileage In the 4.0 and 2.5 Jeeps as well as the 7.5 Ford.
The 3.6 is getting whatever the dealer uses non synthetic. Probably cheap Mobil 1 but not sure.
I’ll start changing the oil in the 3.6 next round and probably move to the Penzoil for that also.

Why Penzoil? IDK been my go to for 25 years at least and the Home Depot has great price on it in 5 quart containers

 

[Rickwhoo]

I have no leaks... Yet

 

[Link]

I have no leaks... Yet

It will.........

 

[HeffTJ]

I don’t know what the idea was behind using such a small oil filter, right when I saw it I knew it wasn’t the correct one.. probably fit so they went with it idk.. ran fine tho haha


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I’m gonna go with 10w-30 mobile one extended performance.. I’m not going to go 15,000 miles between changed.. but it should be a good quality synthetic.. maybe 7000-9000 between changes.. I use either Napa platinum oil filters, mobile one, or k&n..


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I use the NAPA house brand in the red container, (it's actually Valvoline), at the weight printed on the oil cap for my 2005 TJ 4.0 liter. I also use their NAPA Gold #1085, it's made by Wix, which I've used on all my engines. I've heard that the synthetics tend to leak a bit in the 4.0, but since I've never used it in that vehicle, I won't ever know! I'm also old fashion and change oil every 3,500 miles