zebvance

I have a 1988 keep Comanche. Just got it about a week or two a go. It has stock gears and a auto tranny 4wd. It has a 4.5 inch lift and 31/11.50/15's. From filling up I'm guessing has about a 14 or so gallon tank. When I went to fill up again I looked at my trip and how much has I had used. I had used 13.1 gallons and got 144 miles to the 13.1 gallons. That sucks. It was all city driving also. The engine has 103,000 miles. Is this gas mileage normal for this set up on stock gears? On highway it really dosent have much more in it at 70 mph. Could I expect better or worst mpg on highway?

whowey

Well... it has a much larger tank for one thing. The big tank is 23 gallons, the smaller one is 16 or 17 IIRC.

zebvance

Yea I know I read that it was suppose to have that also. It's a swb. But I have filled it up when it was touching the red and got 13 gallons in and by that Tim it had overflowed a little bit.

btm24

I get about 11 if that makes your feel Any better, with the same set up. I also drive with a heavy foot

Brandon

99 Purple XJ

My over head console on my 99 reads 13.1 babying it 32's stock 3.55 gears automatic

zebvance

Ok well I guess mines not far out of the question. I also drive with somewhat of a heavy foot. I guess now I just need to fig out the gas tank deal.

btm24

It's amazing how driving with an egg between you and gas makes your MPG's go up. I found this out in my Sebring, it has the mpg computer on it and it freaks me out when I start to pass some body or any thing else crazy like that. If I drive carful I can get 22-24 if not I get 15-18, so it has alot to do with your driving habbets.

Brandon

BrofessorXJ

Check your header for cracks. It was causing me to lose mpg's big time.

zebvance

I have a very bad exhaust leak. How much of a difference did you notice?

jebmccall

you will notice a big difference, the o2 sensors are not getting the correct info they need.

Zack92MJ

Depends if its before or after the o2 sensor. Before bad. After eh doesn't really matter.

89eliminator

well it is undergeared for one, so that will cause poor mpg. second, its a lifted jeep so you cant expect great mileage. with that said, i would fix your exhaust, and regear.

BrofessorXJ

Exactly. I was getting 10-11 mpg and as soon as I replaced the headers and threw in a new upstream o2 it jumped up to 15-16. Solved my bogging problem after start up and first putting it into drive too which was annoying. Since then I've thrown in an APN header and its done everything I've wanted it to do for $150. A lot stronger too.

That being said, you will never get great gas mileage in a 4.0 it just isn't what they were made for.

My375hp302

Was your speedo corrected after the 31" tires were installed? If not your speedo and odometer are reading slow so you have actually driven farther than your trip meter reflects. That will screw up your math when calculating ur mileage.

BrofessorXJ

Not a ton but enough to notice. Good thinkin.