Sunder the problem lies with the misnomer "hi-test" There is nothing hi about it! All it does is produce a lower flashpoint! So maybe in reality it should be named "lowtest" But since it was invented for big spenders it just naturally came by the wrong name.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

What?? are you saying that higher octane fuel has a lower flash point?

Well I am saying I don't know any other way to explain what Hi-test is for.. We know it waits till there is a higher compression before it will light by itself.. I think the word use is Ok in this non tech instance.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

I'm not sure how to explain this, you two just need to get married. I think I have menitoned this before, but sheese....
Honestly, and I will be happy to do some documenting of actual fuel consumption and at what degree incline I have to down shift just to get up the hill with 87, and even 89, but when I put 93 in there, she zooms around like I've got a Texas tail wind and runnind down hill wehn I am going up a 6% grade or whatever.
Additionally, I don't sit down with a pen and paper or one of those high-tech california calculators to determine how many miles I get for how many gallons.
I use the tank rule. I get 250 miles per tank with the 87, about 275 with 89 and ALWAYS over 400 with the 93. That is enough of a difference to me. Not all 4.0L's are the same.
BigJim, I'm not one of those big spenders. Look at what I just posted. 400 miles per tank vs. 250? I would be a "big spender" if I were to put the cheap stuff in there, and would wear out my clutch with all the hills around here!

SO, Back to the origional post, it varies dude, by gas grade, driving conditions, driving habits and the condition of the engine and ALL of it's components. Good luck and I hope that you have gotten something out of all this....

Let me see some math 250 miles per tank vs. 400 miles. That is a differance of 150 miles per tank. Now I am not sure of you tank size but it is what a 15 gal or 20 gal? On a 15 gal tank 93 octane gives you a boost of 10 miles per gallon. On a 20 gal tank that is a boost of 7.5 MPG.

250 miles/15 gal = 16.6 mpg
400 miles/15 gal = 26.6 mpg

250 mi / 20 gal = 12.5 mpg
400 mi / 20 gal = 20 mpg

Impressive numbers. I didn't use a calculater so correct me where I am wrong.

Cheers,
RJ

RJ I am sorry but the problem here is you did not use Georga addition..
I agree it is voodoo gas milage if you don't calculate it exactly on every tank.. Guessing don't get it.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

Okay, remember, I live in GA....

[quote
]Okay, remember, I live in GA.... [/quote]


<img src="/forums/images/graemlins/smile.gif" alt="" /> <img src="/forums/images/graemlins/smile.gif" alt="" /> <img src="/forums/images/graemlins/smile.gif" alt="" />
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

also for different areas the grades of gas are different in more rural areas there are more poluants in your gasoline... and in more urban areas there are less....watch the discovery channel guys its all on there :P

Gasoline is a fasinating subject. Here is a link to a lot of information about it.
Gasoline FAQ
Now back to the subject of this thread.
In any given year/model, the 4 cyl Jeep will get slightly better city mileage and the 6cyl will get slightly better Hwy milage.
The average mileage will be about the same. I would get a 6 cyl and enjoy the extra power. Another factor to consider is a 4 cyl with a 4 speed manual transmission will get better mileage than a 5 speed. On the other hand, a 6 cyl 5 speed will get better mileage than a 4 speed. (with stock gears and tires) <img src="/forums/images/graemlins/cheers.gif" alt="" />