differential oil question

Can changing to a synthetic diff oil increase my milage?

In theory, you would get a minute improvement, but it would be so small as to be unmeasurable. And the extra cost of the syn lube would probably be greater than any fuel savings you would see imo.

If you own the inline 6- 4.0 there isn't ANYTHING you can do for milage. Many threads on jeepforum-cherokeeforums about MPG. Most people are getting about 16MPG including me.

One thing you can do is a cold air intake either K&N or some other for maybe 1/2 a mile LOL. Also going up in tire size will kill any MPG.


I use Royal Purple gear lube and syn Dextrn. Just because I love to hate my XJ.

About the only thing you can do to get better mpg is make sure everything is tuned up properly, make sure you have no exhaust leaks, especially around the manifolds.

You can switch to shorter tires, or narrower tires, or do both. You could re-gear if you dont already have 3.07s (highest gear ratio ive heard of in an XJ).

One thing I have heard several people agree on is to make sure you have aluminum wheels and lightweight tires. Makes sense to me. I have factory steel wheels and 6-ply LT rated tires, and theyre heavy as crap, takes more power to get them moving....tires for my car are only a couple inches shorter but weigh a lot less because its got aluminum wheels and touring tires.

Most of these things would take a long time to pay for themselves. One free thing you can do is reduce the weight of the vehicle...if youre one of those people that carries around 500 pounds of gear everywhere you go...trim it back a little.