I have just shy of 190,000 miles on my XJ and switched from 10w30 to Rotella T6 and a NAPA filter two days ago. The Jeep runs so much smoother now that I am hearing all the other little noises it makes, including the rattle of the spring in my snow brush

 

Just avoid "Snake Oil" where they tell you that it can be run for 50,000 mi. or some other outrageous mileage numbers.


Personally in my XJ I run Rotella and change often (2-3,000mi.) using NAPA Gold/Silver filters made by (WIX filter) or a regular WIX.

 

Clean filter adapter before new filter, clean oil to lube filter O ring, half turn after gasket contacts. Not condesending, but be sure drain plug is in before filling. Knew a kid from highschool that dumped 12 quarts before he realized it, decades before XJs.

 

Man you just opened a can of worms you'll wish you didn't open.

There is no best oil. Different things work for different people but in reality you could run just about anything in these motors for 300k.

Jump on the 10w-30 rotella band wagon if you wish to go that route, or just run whatever conventional dyno oil you feel. I'm not a fan of synthetic for the 4.0s but that's just me.

A quality filter is more important. I usually run purolator pure ones

 

Bobistheoilguy.com is a much better place to be asking questions like this. Hell, don't even ask. Just go there and do your own research. They have tons of posts, articles, and UOA's to read.

My top three for the 4.0 are Pennzoil yellow bottle 5 or 10w30, Castrol 0w30, or Rotella T6. No particular order. It's not a picky engine at all except for most (not all) Mobil oils showing lots of iron in UOA's.

 

You're saying that the 4.0 isn't a fan of certain Mobil oils? I'm just curious. Read that great big oil post (more like a book) from Salad and remembered that the Mobil One "High Mileage" stuff has lots of zinc...which is apparently what these engines like. Now I have to skim through that again...I used Mobil in my last XJ and never had many problems.

 

Zinc isn't as supremely important/necessary as many people insist on believing. Here is a link to an excerpt from an SAE document (the link that follows) debunking the ZDDP myth.

http://www.steelsoldiers.com/showthr...nd-ZDP-content

http://papers.sae.org/2004-01-2986/

Since I determined that there isn't a single Mobil 1 product that can match or beat what other oils can provide for the 4.0, I've long since dismissed the brand altogether and no longer remember which were the ones that didn't have high iron UOA's. You'll have to research that yourself. The only one I'm pretty sure I remember being OK was 0w40. For all I know, the high mileage formula the Salad has in his post is OK as well, but I don't know how much UOA data Salad used in writing that post either.

 

Thanks for the link, I'll look into it.

 

I see my reputation preceeds me...

Rotella T6 is a helluva lot of bang for your buck. But if you're low on buck, Pennzoil 5w30 in the yellow bottle is an EXCELLENT, well-priced conventional oil. Around these parts its frequently on sale, too.

lmao

I recall reading similar, but that was nearly a year ago.

 

Just out of curiosity what is so wrong with fram filters and why not run high mileage oil? I'm not looking to be attacked for asking, just truly want to know.

 

Sorry man but there are about twelve thousand threads on this subject already. Check out the link in my signature regarding oil. As for FRAM filters... Google is your friend. Simple answer is they're "too good to be true". Cheap garbage.

 

Mobil super is good oil. If the price is right, use it.
Don't get the cheap filter they bundle with it though, get a Mopar, Wix, Purolator, I believe AA carries one or more of those brands.