The Wrangler isn't all that fuel-efficient, even compared to other truck-based utility vehicles; and with its EPA 16-mpg city rating, it could even be considered a guzzler and simply isn't a replacement for a crossover or other family vehicle if you want to keep your fuel budget (and use) down.
But that's of course if you plan to do a long commute in the Wrangler every day. Compared to most dedicated off-road vehicles, the Wrangler's gas mileage isn't all that much worse, though.
It should be noted that with the new Pentastar V-6, the Wrangler's ratings are up significantly this year—up one mpg in either the city or highway, and 2 mpg higher on the highway with the new automatic, to 16/21.
For a vehicle with so little passenger capacity, the 2012 Jeep Wrangler uses a lot of fuel—though for those who truly use its trail capability regularly, it's forgivable.