[tx-Skydiver]

Since moving to 35 inch tires, I've seen my mileage go from 19 to 10.9 on the highway. I knnew I would take a mileage hit, but didn't expect it to be so extreme.

What suggestions do you have to improve this?

[bonedigger]

what gears do you have? I have the 4:10 gears and am running 37" tires and I am still getting 17 mpg on the freeway ( calculated using a gps unit). but to answer your question you can :
1- change gear ratio
2- air intake
3- exhaust

[bryans98tj]

according to his specs its 3:21 gears...that has alot to do with it.

[SecondTJ]

best bet would be to re-gear.

[jeffmarion]

I'm averaging between 14-15 mpg with 37's and have an automatic. I just drive with the O/D off.

[JK_Jeep]

Originally Posted by tx-Skydiver

Since moving to 35 inch tires, I've seen my mileage go from 19 to 10.9 on the highway. I knnew I would take a mileage hit, but didn't expect it to be so extreme.

What suggestions do you have to improve this?

Consider the following,,,,,,

Have you " matched "the new tire size for proper operation of the computer?

Your mileage may be wrong because if your tire size has changed your actual miles driven will be incorrect,,,, lets say you drove 100 miles,,, with the larger tires maybe you actually drove 90 miles (just a figure) but the odometer still shows 100,,,get what I mean?

So I would go back to the first,,,have you corrected the speedometer/odometer for the new tires?

Mileage may not be as bad as you thought

[got_4_lo]

guy above me is right.

you need to come up with the % error of how much farther you're going with the new tires or use a GPS.

[tx-Skydiver]

I actually have 4.10 gearing and automatic tranny. The lift/tires was installed by 4 wheel parts. Do they not automatically adjust the computer for the new tire size?

Also, I am only geting about 200 miles to a tank of gas. When driving to Houston from Dallas (which is not that far) I have to fill up on the way again. I cannot make it the whole way on a single tank.

My RPMs are almost contantly at 3200rpms becuase if I try to keep them at 2000 for overdrive cruising and a small hill comes up, I will immediately lose 5 to 10mph so the tranny kicks down into passing gear.

I've tried cruise control with the same results.

[JK_Jeep]

Originally Posted by tx-Skydiver

I actually have 4.10 gearing and automatic tranny. The lift/tires was installed by 4 wheel parts. Do they not automatically adjust the computer for the new tire size?

Also, I am only geting about 200 miles to a tank of gas. When driving to Houston from Dallas (which is not that far) I have to fill up on the way again. I cannot make it the whole way on a single tank.

My RPMs are almost contantly at 3200rpms becuase if I try to keep them at 2000 for overdrive cruising and a small hill comes up, I will immediately lose 5 to 10mph so the tranny kicks down into passing gear.

I've tried cruise control with the same results.

Again its all in the correction of the computer

[tx-Skydiver]

Originally Posted by bryans98tj

according to his specs its 3:21 gears...that has alot to do with it.

Thanks for the reminder. I changed my profile to reflect my actual vehicle better.

[tx-Skydiver]

Originally Posted by JK_Jeep

Again its all in the correction of the computer

That was my first idea, but I do not know how to go about that. Do I need to buy an aftermarket programmer like a Superchips?

Bonedigger - I also intend on these mods pretty soon as well (except for gear change) so I know that will buy me 1-2 mpg off the bat. Just need more $$$.

[thundercat900]

I have 3.21 gears and a 6 speed. my on vehicle display was averaging 18 or so and after I put on 33's and a 2 inch it went to 14.5. I average around 2000 rpm's on the highway at 65 mph and it doesn't seem to pull hills as good as before.
Thanks god I have a supercharger, without it the jeep would be really bad on the highway. The low end feels great and it feels like it could pull the front wheels at times LOL . I do mostly in town driving so I will probably be upgrading to 4.10 gears to help out.
I was able to help out the mileage and performance with a unichip and some tuning. I would recomend doing a unichip and a custom tune to help out the low end and highway fuel mileage. PM for info.

BTW does anybody have some 4.10 gears they want to get rid of

[VfrRider]

Hand calculate a couple of tanks to get an accurate average. GPS and computer will get you in the ballpark but will not be as accurate as hand calculation.