What oil do you guys use on your 4.0s?


Rubirob

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Hey I’m back and with another question guys. Doing an oil change on the 2004 rubicon I just got. Just wondering what oil you guys run. I got 10w-40 synthetic mobile one high millage. I live in California so we don’t get below zero ever haha.. coldest this Jeep might go is Tahoe/Nevada in the winter.. my 90 Cherokee has the 4.0 and we have always done 10w-40 but in my Haynes manual it says 5w-30 for cold and 10w-30 for normal weather. Guy at the parts store agreed with me that 10w-40 would offer more protection.. you guys agree? There may be a thread on this if so I apologize in advanced haha..

also what coolant do these use? The zerex g-05 50/50? Thanks guys!!


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LJ ken

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I've been using mobile 1 10 dubya 30 for cooler months in a 2.5 yj, 4.0 wj, 06 Rubicon tj, my current Rubicon Lj and a j20. I'm in Jersey so hot summer and cold winter, I haven't had any issues so far and they all seem to like it. I'm not putting out for amsoil.

I personally think anything 5wXX is too thin for the 4.0, but I'm also not a professional nor am I a mechanic. I am open to being learned about this.
 
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Rubirob

Rubirob

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Thanks for the reply, I was thinking I might go 10w-30.. I put 5w-30 in all the 4 bangers I work on.. Honda, Toyota, small chevys.. just is weird to put that in the 4.0.. I feel like it needed more haha


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Rubirob

Rubirob

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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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Rubirob

Rubirob

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I use generic Valvoline. Oil is oil for these 4.0s, they don't care about synthetic or anything like that. What matters is the correct weight, that's it.

That is very much how the 90 4.0 is, it didn’t really care haha. I just am trying to treat this Jeep right! So 10w-30 too Chris?


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Rubirob

Rubirob

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Rubirob

Rubirob

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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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My chevy 5.3 v8 runs on Walmart 5w30 synthetic, here in Florida, so I figured it was good enough for my TJ 4.0. My TJ oil pressure is 40lbs at an idle. Also, here’s a TJ 4.0 hack for a bigger oil filter.


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Davidtj

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My chevy 5.3 v8 runs on Walmart 5w30 synthetic, here in Florida, so I figured it was good enough for my TJ 4.0. My TJ oil pressure is 40lbs at an idle. Also, here’s a TJ 4.0 hack for a bigger oil filter.


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On oil filter hack I wonder if internal by pass spring pressure is the same ?
 
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ac_

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I run full synthetic in all my bikes, TJ gets 10w30 dino NAPA with mopar oil filter and 3k oil change intervals.

You will get a lot of varying opinions here.

+1 here except I don't use synthetic in my bikes, but does not matter here anyway, but I do use 10w30 Valvoline/Napa dino with mopar filter in my Jeep every 6 months or 3K whatever comes first.

just in case you are interested:
All of my bikes regardless of makes get 10w40 Yamalube.
 
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Rubirob

Rubirob

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I just had to go to dealer to get the left Column multi switch.. Napa one didn’t work.. asked the guy behind parts desk and he said 10w-30 just for everyone’s info lol


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Kiwi TJ

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I use black stuff..lol
I always thought that the 4.0L were pretty much bullet proof so I run Castrol Magnatec 10w 30...works great.
 
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On oil filter hack I wonder if internal by pass spring pressure is the same ?

I have no clue, I guess that data might be out there somewhere, just don’t know where. I’ve been running that filter for about a year and have had no problems.


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Chris

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That is very much how the 90 4.0 is, it didn’t really care haha. I just am trying to treat this Jeep right! So 10w-30 too Chris?


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Yep, I run 10W-30. I'd only run 5W-30 in the Winter months if you lived somewhere where it got really, really cold!

But other than that, any brand works. These 4.0 engines are not high performance engines that require synthetic or anything fancy. You can get 600k plus miles on just regular, conventional oil.