So, I rlaced my factory go-kart tires with some 285/75R16's and my fuel economy plumited from 21 to 14.5. I replaced my 3:21s with a set of 4:10's and it did nothing. The jeep has been recalibrated and the throttle body was cleaned a few weeks ago.

Stats: 2007 Wrangler X, auto tranny and 33's with 4:10 gears (yes I am sure they are 4:10).

Does anyone have any suggestions? I know that bigger tires always mean worse gas mileage, but it shouldn't have dropped this much.

 

BFG AT with 30psi notrogen (i get it free)

 

Well damn something isn't right... I'm running 35's and 4.10's and getting over 15mpg. Did you recalibrate your speedometer? And is it accurate?

 

Is this according to your calculations or the Jeep's?

Have tested the speed with gps?

 

Your MPG's shouldn't drop like that. Even with 37's and 4.10 gears I'm getting 16 (hand calculated) maybe try and calculate it by hand and see if you get something different. These jeeps are known for having improper readings.

 

My calculator and I did check my speed with gps before and after the calibration

 

With 37s 4.88s and a 6spd I get 12 when u had 33s ans 3.21s I got 15 when I had 35s and 3.21s I got 14

 

When it was stock I was getting 18 max hwy and 16 in town. The first week I owned it I was getting 18 in town and 22 hwy but they put a new motor in it at 400 miles and then mpg dropped alot.

 

Wow, 12? I'm thinking about making the jump to 4.88 and 37s someday but I dont want to see that number. I am a little lighter than you, I guess that would help. Interesting.

 

Do tell how...