Jeep 4.0l i6 What oil should i use?

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Im new here to the forum, after reading the 101 write up and looking through all the posts i decided to sign up. Now I know its been asked a bunch of times and I've been searching this topic for days but I feel like the more I read the more confused I get lol.

Im a noob when it comes to oil in fact I've never done an oil change before but people keep telling me how easy it is and I'm a firm believer of the old "if you want it done right, do it yourself" moto.

I have two jeeps, the grand cherokee my girlfriend drives on a daily basis and my wrangler is a "weekend warrior". The WJ (grand cherokee) ive owned for a year now and the TJ (wrangler) I purchased last summer. The WJ has 138k miles and the TJ has 116k miles. I only put about 300-400 miles per month on the TJ, the WJ sees 500-600 miles per month, both of which consist of mostly city driving, short trips, idling (remote starts in both), etc. We live in Mass. and the temps throughout the year are typically between 10F and 90F rarely less and rarely more.

I've only had the oil changed once when I first got them (the WJ needs one very soon). The mechanic that did it used 10w40 in both (TJ has synthetic but im not sure about the WJ and have no clue what brand) The WJ has always had that slight tick to it that sounds like a lifter or something but recently I've noticed it sounds terrible especially at start up but there's still tick when it warms up and sometimes it even vibes at a redlight.

My TJ seems to be running fine (besides the fact I think my oil sending unit has gone bad )but the WJ has that terrible tick that turns my stomach. I've come to the conclusion that the oil might be too thick as the manual recommends 10w30 (its winter too) and have read in most forums that they run this sometimes 5w30 and others say they run rotella and that their engines like thicker oil. Ive also read in alot of places that fram filters suck and im pretty sure thats what is in the WJ (I'll have to confirm this). And if this information matters the radiator did blow on the WJ a couple of months ago... but i got that fixed on the spot!

I would like to run the same oil and filters in both and start doing my own oil changes. Im thinking of using QS Defy 10w30 as people say the little extra zinc is good, and am thinking of using a K&N performance filter as i've only heard good things about them.

Something I've been wondering too is since the engine requires 6 quarts oil, could/should I use 5qts of "x" and 1 qt "y". Ive heard of people using 5qts oil, 1 qt additive or something like 5qts 10w30 and then a qt of 0w40 to get something like "8w32" or does it not work that way and just put 6qts the same?

And last but not least intervals? it takes a while for us to put any real mileage on the thing should i change every "x" amount of miles or change every "x" amount of months?

Another note too is i believe the WJ has some leakage because everything seems to be coated lightly in oil the top of the engine, underneath, etc. I've checked the level of oil and it seems okay even after w.e the interval was.

Again sorry for the 21 questions and long write up but I'm really confused
confused.gif
 
Welcome to the forum from another Jeep 4.0 owner!

4.0s are noisy- don't let valvetrain ticking worry you unless its really loud and "heavy." Be aware that an exhaust leak at the head-to-exhaust manifold junction can sound a lot like a ticking lifter except that it will get louder as you press the gas pedal and will go quiet when you lift off. A ticking lifter won't do that.

They're not really picky about oil, either, though most 4.0 owners err on the thicker side rather than thin. I wouldn't try a 5w20, for example... but a 5w30 or 0w30 should be just fine. I live in hotter country and run Rotella T6 5w40 year round, but for your area something like M1 0w30 should be great if you want to go full synthetic. Nothing wrong with the QS Defy you mention, either, although my pick would probably be Pennzoil yellow-bottle 5w30. Unless you just WANT to, I wouldn't fool around with mixing up a concoction. Just use a quality oil right out of the bottle.
 
I've used Castrol GTX HM on two 4.0L's and they loved it. They also run good on Valvoline Maxlife. Use a 5w30. For 4-5k OCI on conventional. I've never run a full synthetic in them so I can't recommend an interval on that.

I've heard that the only oil the 4.0 does not like is Mobil 1.
 
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I've been running 5W30 Maxlife Synthetic in the '98 XJ 4.0, seems pretty quiet & starts easily cold. When the hot weather returns, I'll switch to PYB again.
 
Originally Posted By: Nick1994
I've used Castrol GTX HM on two 4.0L's and they loved it. They also run good on Valvoline Maxlife. Use a 5w30. For 4-5k OCI on conventional. I've never run a full synthetic in them so I can't recommend an interval on that.

I've heard that the only oil the 4.0 does not like is Mobil 1.

I was also considering mobil 1
blush.gif
but I'll cross that off my list since youre not the first person to tell me that.
 
Originally Posted By: jbotelho15
Originally Posted By: Nick1994
I've used Castrol GTX HM on two 4.0L's and they loved it. They also run good on Valvoline Maxlife. Use a 5w30. For 4-5k OCI on conventional. I've never run a full synthetic in them so I can't recommend an interval on that.

I've heard that the only oil the 4.0 does not like is Mobil 1.

I was also considering mobil 1
blush.gif
but I'll cross that off my list since youre not the first person to tell me that.


Don't be so quick... Mobil 1 did just fine in my 4.0s before I switched them to Rotella. Some people report that they are noisier with M1, but that has not been my experience at all. I still think that M1 0w30 would be just fine for your application.
 
Originally Posted By: 440Magnum
Welcome to the forum from another Jeep 4.0 owner!

4.0s are noisy- don't let valvetrain ticking worry you unless its really loud and "heavy." Be aware that an exhaust leak at the head-to-exhaust manifold junction can sound a lot like a ticking lifter except that it will get louder as you press the gas pedal and will go quiet when you lift off. A ticking lifter won't do that.

They're not really picky about oil, either, though most 4.0 owners err on the thicker side rather than thin. I wouldn't try a 5w20, for example... but a 5w30 or 0w30 should be just fine. I live in hotter country and run Rotella T6 5w40 year round, but for your area something like M1 0w30 should be great if you want to go full synthetic. Nothing wrong with the QS Defy you mention, either, although my pick would probably be Pennzoil yellow-bottle 5w30. Unless you just WANT to, I wouldn't fool around with mixing up a concoction. Just use a quality oil right out of the bottle.

I think it gets quieter when I accelerate its mostly at low rpms, loudest at idle for sure. To better describe the noise I personally thought it sounded like a worn out belt but everyone says it sounds like lifters, Ive gotten the belt inspected too just in case and its in good shape I think it was replaced when i got it (cant remember).
 
Originally Posted By: 440Magnum
Originally Posted By: jbotelho15
Originally Posted By: Nick1994
I've used Castrol GTX HM on two 4.0L's and they loved it. They also run good on Valvoline Maxlife. Use a 5w30. For 4-5k OCI on conventional. I've never run a full synthetic in them so I can't recommend an interval on that.

I've heard that the only oil the 4.0 does not like is Mobil 1.

I was also considering mobil 1
blush.gif
but I'll cross that off my list since youre not the first person to tell me that.


Don't be so quick... Mobil 1 did just fine in my 4.0s before I switched them to Rotella. Some people report that they are noisier with M1, but that has not been my experience at all. I still think that M1 0w30 would be just fine for your application.


Ive heard that about mobil 1 hm specifaclly their 10w30 which is the grade ive been leaning towards. I'd prefer to use the same oil year round as it doesnt get changed too often. You think a 5w30 is good in the summer months too? I feel like 0w30 might be too thin for sure but idk. summers here are typically between 80-90 occasionally 95 maybe even 100 but its rare
 
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My 4.0 engine was very noisy with M1 oil.

I am currently using PYB and it's all quiet. T6 or quaker state defy are both something to consider IMO.
 
Originally Posted By: jbotelho15
Originally Posted By: 440Magnum
Originally Posted By: jbotelho15
Originally Posted By: Nick1994
I've used Castrol GTX HM on two 4.0L's and they loved it. They also run good on Valvoline Maxlife. Use a 5w30. For 4-5k OCI on conventional. I've never run a full synthetic in them so I can't recommend an interval on that.

I've heard that the only oil the 4.0 does not like is Mobil 1.

I was also considering mobil 1
blush.gif
but I'll cross that off my list since youre not the first person to tell me that.


Don't be so quick... Mobil 1 did just fine in my 4.0s before I switched them to Rotella. Some people report that they are noisier with M1, but that has not been my experience at all. I still think that M1 0w30 would be just fine for your application.


Ive heard that about mobil 1 hm specifaclly their 10w30 which is the grade ive been leaning towards. I'd prefer to use the same oil year round as it doesnt get changed too often. You think a 5w30 is good in the summer months too? I feel like 0w30 might be too thin for sure but idk. summers here are typically between 80-90 occasionally 95 maybe even 100 but its rare


5w30 and 0w30 are both 30 grade oils, and perform essentially identically (except for small variations among brands) at operating temperature. Frankly there's not that much difference until you get to sub-zero temps where 0w30 thickens up less than 5w30. So no difference in summer, maybe a little advantage 0w30 on the coldest winter snaps you get in MA. Just as a "for instance," my Ram 1500 calls for 5w20 oil. But since 0w20 has come out I sometimes run it, including towing at highway speeds, in Texas summers. I've towed ~4000 lbs of trailer plus another 800 lbs or so of cargo, in 110F ambient temps, on I-10 at the 80mph speed limit, with 0w20 in the sump, and not observed a single pound of pressure drop on an accurate aftermarket oil pressure gauge. Then an oil analysis afterward turned up perfect. The 0wXX grades really work as advertized. do I NEED 0w20 in Texas? Nah, not except for the SRT which is spec'd for 0w40 and so I don't run it in the Ram routinely. But it does work.

10w30 is pretty much an archaic grade, as is 10w40. There are a few niche applications where those grades make sense, but for the most part they're obsolete. Frankly I think some oil blenders use them as a dumping ground for low viscosity-index base stocks, but that's just conjecture. 5w30, 5w20, 0w30, and 0w20, and 0w40 are the grades where the technology push for passenger cars is at among the mainstream brands. 5w40 is still in the forefront for heavy duty applications.
 
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Originally Posted By: Chris142
A common tick in the 4.0 is the oil pump driveshaft. Its bushings wear out and it sounds just like a lifter. Another one is a broken piston skirt. Its not caused by 10w40

perhaps this is something i need to look into. If this is my problem how hard is it to replace?
 
The 4.0 engine is a tractor engine. Not too picky. I use Rotella T6.

No oil will prevent the 331 head problem or cracked piston skirt problem.
 
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You have 2 2004 engines so you should be fine. 2002 and older had the 0331 issue.. Although later 2002s are fixed as well. Fun fact. Shine a light into your oil cap. It'll say Tupy.. The updated heads are made in Brazil of all places.

Not too sure on the cracked piston skirt, but from what I've seen over at Jeeps Unlimited, it's the 99-02 that had piston skirt failure as well. Could potentially be any years though I suppose. You'll know if you have that issue.
 
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Having owned 3 vehicles with this engine and done UOAs, I agree with steering away from M1 0w30 or 5w30, not only for the noise but also more than double the iron produced in the course of a 5000 mile run. Do not know about the HM 10w30.

Any major brand 5w30 will serve you well throughout the year, and a 0w30 will help with flow at startup in most cases and temps. There have been a couple of fantastic UOAs with 10w30 recently; but for your location I wouldn't be using a 10wXX in winter.

but..

Since you asked about change intervals and want to use the same oil for both, AND the driving styles of both vehicles are so different, I can recommend Amsoil SS for both. A one year/10k interval would probably work well.
 
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Hi! A lot of good advice here.

Although I have used everything from SAE30 to 15W40, I have settled on group III synthetic 5W30 in my Jeeps. My '92 is only used off road and to haul wood at home and the 5W30 has shown decent wear numbers compared to the thicker oils (even after use in Moab, UT). I have been tempted to try Mobil 1 0W40 though!

Regarding the oil pump driveshaft, technically the 4.0L does not have one (ex: like an Oldsmobile V8). The distributor connects directly to the oil pump. The shaft in the oil pump can sometimes make noise.

There are a lot of experienced folks here and quite a few Jeep guru's who love to help. Welcome to the party.
 
Thanks for all the tips guys! I think I'm leaning toward 5w30 and 10w30. I think I might try 10w30 next change and see how it likes it since its the factory recomendation and is already thinner than what i have now. If it still doesnt like it Ill be trying 5w30. As for brand Im still not sure but I think I am leaning towards the QS Defy still
 
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