Jeep can't adjust your tire size they can only do the stock size and one or two larger thats it. You have to purchase a programmer like superchips to manually put your tire size in it also has economic settings for different octanes and such. I just wrote this on another forum funny but with 31-32.5" tires you need to add 1-2 MPG to what the computer says. So if it's saying 13 you're probably getting 14 to 15 MPG.