So I just picked up a used 1995 jeep Cherokee with 165,900 miles on it. I'm the third owner and the two previous owners took care of it and were older and never offroaded in it. Currently there are no leaks or anything. Head gasket is replaced. Trannys fine. The only thing is that the previous owner said

"I used high mileage synthetic 15w40"
and he told me its due for a oil change in two weeks

Now, I'm a vw/euro car person so a jeeps new. When I heard synthetic I was thinking that's really good! But reading around Im finding out synthetic oil in high mileage jeeps aren't that great after all.

Some people say it will cause leaks or it will hurt the high mileage engine. Others say if ur already useing it then continue to do so. Personally I want what's best for the engine. I plan on doing an oil change Saturday. Should I trust the previous owner and use synthetic? Or should I stop using the synthetic and go to a thicker standard high milage oil? If u guys don't suggest this "synthetic 15w40" what do you guys suggest? I searched and came up with nothing. Thanks!!

 

You searched and came up with nothing?
Impossible..

Ive literally sat here and watched like 3 "what oil should I use" threads come up..
Not to mention the 32515616634732541 threads about oil that were made in the last month.

 

^^Thank You For this^^
There are way to many. "What oil should I use" threads.

 

I wouldn't change is that's what they have been using. syn or not the key is keeping oil changed regularly. you can run any syn oil in it, doesn't have to be the same brand.

seems like every reply on this forum is "search dude" lol...

 

Wow guys thanks for the response. But before you get all butthurt about me asking "which oil should I use" maybe you should actually take a minute out of you busy busy days and actually READ. I'm asking if 15w-30 synthetic WILL or WILL NOT hurt the 165xxx engine. Throwing in what you guys suggest at the end was just a quick last minute thought. So, before you come and write on my threads change your tampons..

Thanks

 

15w-40 synth or 15-30 synth will not hurt your engine at all. Get a good filter (Wix, Napa Gold, Mobil 1) NOT FRAM and your jeep will run longer than almost any other vehicle on the road.

 

But continuing using synthetic, will this make the motor wear quicker? I'm aware synthetic generally doesn't need to be changed as often as regular oil (regular oil 3k/syn 5k) but i would be changing it every 3K just to be safe. If syn oil wasn't made for these engines I won't use it. But Im unsure if I can just switch to another oil and have a slight mixture of syn/regular oil, I can't imagine emptying the oil pan will get all the oil out ya know?

And seriously, if u don't want to answer the question just move on. Lol

 

LOL....I like this guy^^^^^^

 

Id say use the synthetic. I run Amsoil in my 06 turbo jeep grand cherokee srt8, 99 tj, 94 saturn and my wifes 02 celica. I have 19x,xxx on mine when I got it 2 months ago and he used synthetic. Which I was going to use synthetic anyway after I get all the oil leaks fixed....lol

 

IMO no syn doesn't last longer. the filter can only filter so much, that's the issue not oil. so if the filter can't filter all the crud syn picks up (better than conv) then it's time to change. SYN basically gives you better protection from dry start. (sitting all night) I would use syn and change 3-4k or 3-4 months, but that's me. I do that in all my toys, but obviously the dirt bikes quads SxS get more often than 3-4k more like 3-400 lol.

if money is an issue you can get good a syn blend. I'm not sure what oil people are running in the 4.0, but I use rotella in my toys. Motorcraft in my V10 because it's a special weight.

lol ya I know 10-15 new threads are answered with "search" honestly on the Tapatalk search sucks and doesn't pull up anything...

 

Are these brands available at local stores(ie. autozone/advanced auto)? Whats wrong with fram if you dont mind me asking, i use fram in my 2007 big turbo gli haha. i read the filter is a ***** to get out on the 4.0 i hope its easy done then said haha

Ive been on so many vw forums im used to "e-bullys" trying to flame me. gtfo go cry about it haha

Amsoil, is this a brand they sell locally? i was always a castrol guy

Thanks for the info dude! and ill prob stick with synthetic i dont get why people says it causes leaks tho

 

I run high mileage castrol 10w30 got 200,000 still going strong . ive run castrol in my last three vechicles nomotor issues ever . jm2cw

 

The filter is easy to change....person who said it was hard to change must carry a purse.....

Amsoil distribution warehouse is here in Lancaster, but unless there is a guy selling it or store selling it no, places like Advanced auto, autozone dont have it

 

Check your attitude. You asked a question that is still asked commonly...syn or not.. You may have searched but you obviously didnt do a good job. Here..this wasnt that hard btw.

https://www.cherokeeforum.com/f2/oil...ic-not-107638/

https://www.cherokeeforum.com/f2/wha...d-i-use-42222/

https://www.cherokeeforum.com/f2/swi...ntional-36772/

https://www.cherokeeforum.com/f59/sh...ine-oil-83702/

https://www.cherokeeforum.com/f2/syn...-fluids-45610/

Want more? Let me know.

SEARCH

 

no problem! well when you have ran dyno oil it builds up sludge more, then syn cleans it all out and take gaskets sometimes with it lol. like a tranny flush at 100k... if you have done regular maint on it, just change the fluid... same thing.

but if it's used to syn I'd stick with that.