Hey,

I've never changed the oil in my cherokee, mainly because there have been other things that have needed to be done and that it hasn't been driven. However, I don't know what type of oil the last owner used for the cherokee.

I've been thinking of putting in some 100% synthetic oil and was wondering if that might be a problem if it has been running mineral oil before?

 

Shouldn't be a problem, unless the engine is full of sludge. Since synthetic generally cleans well, it may remove some sludge that was "covering up" a leak. So, contrary to legend, synthetic oil does not cause leaks, but may uncover a leak that had been "hidden" by deposits.

 

Ah, sounds great! And I guess that it's also a myth about how old engines run better on plain mineral oil rather than synthetics? Or are some addetives actually helpfull?

 

I think with these engines (4.0), they will run well on any quality oil.

 

Get an oil with zinc in it or find an additive with zinc. It's good for the lifters in the 4.0

 

Hmmm...I take Zinc when I'm sick. Good to know the Jeep and I can be healthy together with this "additive"

 

Running oil is recommended lol. These engines haven't really changed since they were brought to market in 1964. One of the best oils for the 4.0L is actually a synthetic diesel oil (Shell Rotella T6); they will do very well on any diesel oil. The heavier viscosity is ideal for these old engines and diesel spec has a high zinc content. Most diesel oils are actually certified for use in gasoline engines too. Of course treat it right and run of the mill 10W30 will get you to 500,000 miles. Not sure what your options are in Sweden but looking into a synthetic diesel with low startup viscosity (5W40 is good) is a good bet for longevity.

Actually more important than the oil is a quality filter. If it's priced very low you can bet the quality is also rock-bottom. Here in North America FRAM, STP, and the types installed by quick lube shops are very bad. WIX, Purolator, or any of the performance filters (if you care to spend the money) are preferred.

 

Wow great tips! I didn't know that about diesel oil, even though diesel is quite popular here (and in europe). Most people run a 5w40 or 0w40 because of the cold weather we get around winter times so i'll probably run 5w40 since that is the most common type of oil.

The filter though i knew about, i'm heading to the states in the beginning of november for 3 weeks so will be picking up quite a bit of things for the XJ there, a purolator gold filter will definately be added to my list probably 2 or 3 !

 

Changes my oil today on my 2002 GC. Used 5w30 I love in Connecticut and it's beginning to get colder, so I went from 10 to 5w. I used a Wix filter and 6 quarts of Royal Purple full synthetic! Never get a fram filter. Ever. Stay with Wix, Napa gold/platinum, or even Purolator

 

In my opinion, there is no reason to start running an expensive synthetic oil on a 25 year old engine. More than likely it had dinosaur oil it's whole life and if it's lasted this long, why spend three times as much running synthetic oil? I run 10w30 in my '87 and use the block heater in winter.

Now, if you have done an engine overhaul and are more or less starting with a fresh engine, then it might make sense to use sythetic

I have a '67 GMC pickup as well. It still runs on dinosaur oil and that's all it ever had. Original engine. I just make sure the oil filter is changed regularly and use a good quality Wix filter with it.

On a modern engine, especially a 4 cylinder, high revving engine, I would be tempted to run synthetic. My Toyota is 0W20 synthetic from the factory so I will continue to run that.

 

So would using the Rotella T5 I think it is in a 10w30 be good? I'm in Indiana and probably doing a rear main and oil pan gasket this weekend with oil change. I think the T5 is a synthetic blend.

 

T5 can be synthetic blend, depends on which T5 you get. I believe Shell's ratings are to do with wear performance and the additive package. 0W30 and 0W40 are both full synthetics sold under the T5 label.

Myself and a bunch of other people here run T6 5W40.

 

Dealing with my failed 2001 XJ 4.0 Pre-Cat issue and reading about additives and high Zinc content contributing to catalytic converter death, should I be worried about running a diesel oil like Rotella or Delo because of the Zinc and my finicky, poorly designed factory dual pre-cat system???

 

I run the t6 rotella oil with the bigger wix filter (15151 or something). I don't go offroad so the longer filter only brings positive attributes. if your jeep doesn't leak oil, synthetic is a good choice because of the extended change intervals, simply bc of that the cost is offset. not to mention t6 isn't *that much more expensive than a quality nonsynth.

 

T6 can be found at local wholesale stores (ie Walmart and the like) for a few dollars less then a parts store, except when parts stores have it on special. The filter, as long as its atleast the purolator classic, is more or less needed. Fram and other crap brands will kill the motor faster thsn you can blink. So basically, yes you will spend about 40$ on an oil change, but if your like me and your toy is also the dd, that 40 bucks saves you in the longevity of the motor.

Also, royal purple is a no no. Recent tests show its pretty much crap as far as quality goes