RumBar

I have the 6 speed with the 3.21 and stock 255 70/17's but I'm planning to move up to 295's with 1.5" spacers and a leveling kit will this be to much of a strain on the engine and have really slow take offs? Will it kill my 19mpg I'm getting? I commute 80 miles a day mostly 70mph highway. Is the there a happy medium with a smaller tire? 265, 275, 285?

tpm152

I am keeping my tire size with the stock size 255/75/17s when my stock tires wear out because just like you my JK is my daily driver (so fuel economy is very important to keeping my JK affordable). The main reason is that if you get the Silent Armor tires in that size they are reasonably priced (~$130 apiece compared to $200+ for most upsized tires). Also in order to maintain speed on the highway I periodically am running near full-throttle up some hills, so any increase in tire size or weight will probably cause me to need to downshift from 6th on the highway: thus killing my current 20+ mpg fuel economy.

So in short my suggestion for you is to stick with stock size tires with the 3.21 gear ratio if you want to keep your current level of MPG.

RumBar

That makes sense and saves cents!

gersh10

Well that's been my dilemma. I'm running and auto JKU, 3.73 gears with the Moab wheels and 255/75/17 BFG M/T'S and have been averaging 19mpg mixed driving and have run up to 22mpg on the hwy... I really wanted to bump up and 1.5-2" in hight and go to 33's but it's my daily driver and at $70 a fill up I'm looking to save every penny possible...
Been looking at going with the either the BFG AT/KO's or Goodyear Silent Armors.
I also have been looking at the AFE air intake and possibly exhaust to help with power and fuel economy.

So any experience with intakes and or exhaust helping with mpg?
How much of a killer on mpg is bumping to 33's with a small lift?
I have the Garvin Expedition rack for my Jeep but took it off after a month + when my mpg's went from and average of 18-19 to 14-15...

hubertron

I get 18 with a mix of city and highway with my 2011 6 speed rubi.

It's about the gas pedal, coasting, and gear selection. 35 mph speed limit on flat? I am in 4 th gear.

JeepMan69

I put 5.13s in my 09 jk unlimited. Running 35s my gas milage went from 12-13 mpg (stock gears) to 16-17 mpg.

achi10

Dude, that's pretty cool! I just put 5.13s in my 2011 and I dipped about 3-4MPG. I'm not at 12-13MPG/average.

I'm running 35's too, what's the difference? What am I doing wrong? =X