I have a 2012 JKU Auto sport...the ONLY reason I went with 37inch TOYOs is that the guy at the 4x4 shop said that the MPG's wouldn't suffer that much if I did the proper regear. I PAID for the 4.88 gears and AEV Procal and 4" Teraflex lift but I'm only getting around 12-13 MPG! I don't go above 65 and don't have a lead foot.

Is everyone else that have the same setup getting the same MPG? I trusted the 4x4 salesperson thinking I would still get around 16-17mpg. If I would've know the MPG would suck so bad I would've gone with 35's.

 

It's a jeep. Your driving a brick on wheels, it's not going to get good MPG's. And I hope you beefed up that front axle after you installed those 37's.

 

i didn't do the front axle just yet. My 05 TJ had 4.56 gears and 35's and still got 18-20mpg. Everyone said the new engine was much better but I'm not sure now.

 

You shoulda gone to 5.13s. I have them with 35s and still get 16. With that size of a tire, even with the new engine, 4.56 isn't going to cut it. If you had the 44 up front I would day 5.38, but since you don't, 5.13s would have been the way to go. At least get you somewhat closer to where you want to be, but not 17-18, depending on terrain and climate.

 

37s are a different world. You need to make a dew more mods. Did you trim the pinch seam in the back ? You have to beef up your front end if it's a rubicon if not you should change the front axle to a stronger one before doing gears on a dana 30 because it will break.

 

It seems like any way I go I'm screwed....go down to 35's with 4.88's and get worse mpg or end up spending the cash to regear AGAIN! FML.

Anyone out there with 37's 2012 auto 4.88gears, please let me know what kind of mpg's youre getting.

 

I thought the 4.88's would bring the power back to about stock but it feels really sluggish too. Is there a way to check and see if they installed the right set of gears?

 

I did some quick math and those toyos weigh 93lbs plus say 25-30lbs for the wheels. Thats a ton of rotational mass to push around. That alone will hurt fuel efficiency somewhat significantly. That and the fact your TJ was probably a good 400-800lbs (Depending on mods) lighter than your JKU contributed to it getting better mpg.

 

I've got an 08 with 35s and 5.13 gears. It gets about 13 mpg. This is with CA intake, aftermarket exhaust, and a programmer. I question 16 to 17 mpg. I will say that I got a bunch of other weight as well, like, roof rack, front and rear heavy bumpers, winch, and rub rails.

 

Toyos are real heavy tires. Might want to trade them in for say km2 or Mtr. Toyos also run pretty close to actual size whereas the km2 run a little smaller.

You more then doubled the rolling mass of your wheel and tire combo from stock. Did you really expect to keep the same fuel mileage?