Reading over this article they don't seems to have made any exciting change to the fuel mileage on a brick in the wind.....
Explore Jeep Capabilities | Fuel Efficiency (MPG) | Jeep

Even with mod's and lift I am still at 12 mpg city and 19 mpg hwy with the proven in line 6...

 

I have a 2013 2 door sport, and I do 36km 1 way commute spurts. Around half is city half is highway. I average around 21mpg with a 6 speed manual. If I do a long highway drive I have gotten it upto 22.9mpg+. Tricks I've learned don't go over 110km/h (120 the brick makes alot more noise) and don't roll the windows all the way down at highway speed, half way is about maximum. Sunrider position for the top doesn't effect the fuel milage as much. Full top down you will be getting 17-16mpg highway.

This is from personal experience with over 9000kms on the odo.

Edit: i see they say 390 miles or 630kms on a tank. Yeah no.. the system will start yelling at you way before then. I get to around 550kms and the fuel light comes on. I fill up and I get 50 - 60 litres into the tank Theres still a good 15 litres left in the tank.

 

I have a 2012 jkur with 33's,2.5" lift and 4:11's. I have reset tire sizes with the procal. I can avg 11-12L/100k (24-26 mpg imp) driving 90km on the highway and 14-15 (18-20mpg imp) avg around town. this is taken off the dash. I have a steel wurx bumper with a winch on the front which adds a little weight. I went on a 4000km trip through the blue ridge and smokey mountains last summer with wifey and 2 kids and loaded with gear with the stock rubi tires and no lift. Did mileage by hand and my best tank was 26.4 on the blue ridge parkway where u can only do 60-70 km, and my worst was 18.9 climbing mountains on the interstate. I was driving for gas mileage most of the time ie egg under gas pedal. A 2 mpg increase at 20mpg is 10%, a 2mpg increase at 10 mpg is a 20% increase. I would say the new bigger heavier jeeps are doing ok on the gas mileage side. If u use US mpg my figures drop to 22 and 15.7 but i live in Canada. Now, if i can beat it everyday, put it under water twice and lug it through mud every weekend and still get 250 k on it with no problems like my 87 and 91 inlines, has yet to be seen, and highly unlikely.

 

17 city / 21 highway...

But those are US figures. my sons 2012 JKU Sahara gets well over 20 on the highway in real life. I think the new 3.6 has made huge gains.