Mines not a Rubicon, but my 2012 Unlimited Sport Auto w/3.21's 2500 miles saw around 16 to 17mpg's with the stock steel wheels and radial rubbers. Now with the upgraded 33x12.5 17's I'm lucky to 14.5 mpg. Fortunately, I didn't buy my jeep for it's outstanding fuel mileage, but for it's awesome offroad capabilities!!

 

Mines a 2012 Rubicon JKU with 4.10 gears and I get around 16.5 around town and 18ish on the highway according to my manual calculation, EVIC and a scangauge. All are right on and very close to each other.

 

Lifted mine last week 3.5". I'm on 35's and averaging about 18 mpg unless I'm driving into a headwind and then it seems to drop to about 16mpg.

 

Rubi 4:10s auto, 2' lift, stock tires with hardtop. Got 20 mpg on the freeway portion of a long trip goint 70 mph with 350 miles on the JK, returned with 1000 miles on it. Average about 15 around town that includes only short freeway portions.

Very happy with the mpg. Same duty with my 2006 LJ Rubi 4:46s, 33's, 4" lift, skids and bumpers was 14-15 on the long freeway trip, 13-14 around town.

 

Mine is a stock 2012 limited rubicon with 1400 miles on it and its showing about 20.2 on hw and in town was 17, gonna run my own numbers and see how close the puter is. hope a 3.5 lift and 35 wont kill it much.