Okay. I'm going to sound dumb but where is the control to enable/disable OD on 2012 JK? I see ECO light come and go automatically depending upon how i'm driving.

 

Not dumb from my point of view because i am wondering the same thing. i had never even looked before, but just did look for it after reading this thread earlier. Did not see it anywhere. Wondering if it is an option in the settings menu in the cluster??? not sure

 

you don;t have an OD button on the 2012's.

I have 315 75r 17 bfg AT's with a 3.5" lift on my 2012 JKUR with 410's. At the higher altitude here, I can still get 15.8mpg avg. if I drive nice. 5 speed auto.

 

The '12's have variable cam timing and a flatter torque curve, dont they?

For my '07 3.8 6-speed, turning 4.10's and 32's (similar final drive to a '12 auto) - the optimum highway speed is 2,400-2,500 at ~65mph. Above that, wind resistance comes in exponentially quick. Below that, power falls off and I need a little more pedal to make hills. I'm splitting hairs on that side of things, but I clicked off some 22.x (calculated) tanks sticking to these rules. I recently upgraded tires to 265's, and that simple change was enough to throw things off. Still trying to find that sweet spot again.

I'm not sure how the torque curve of the 3,6 is, but I'd try to get a feel for where the motor feels most lively and needs the least amount of pedal for a reasonable speed. I would likely rule out anything over 70mph.

 

On the 2012s with automatic, you turn off O/D by tapping the stick once to the left. Turn it back on by tapping it to the right.

 

i got 20 mpg on a 1,000 mile freeway trip to utah going 70 mph when i only had 350 miles on the JK starting the trip - all stock except the 2" lift. 4:10s with auto. around town its about 15 mpg.

 

Tapping the shifter only shifts down a gear. There is no "overdrive".

 

Stock 2012 auto, average 17.4mpg city/highway driving about equal.

 

There IS an overdrive in the 2012 automatic.. It's 5th gear. The ratio is 0.83, which, by definition, makes it an overdrive.

 

18.3 MPG is very impressive. Is that number accurate .. aka.. Have you calibrated your speedometer to compensate for the bigger tires? You might be getting even better "real" MPGs because 1 mile on recorded on speedometer with 35s is longer than 1 mile recorded with 31/32s.