These aren't Prius numbers, but they do make the four-cylinder Wrangler the most efficient version of the off-roader so far. The rest of the Wrangler range with V6 power gets 20 mpg combined, with the exception of the manual four-door, which gets 19. The most efficient V6 models in the city are the automatic models, which, regardless of length, get 18 mpg. On the highway, the best V6 is the manual two-door, which manages 25 mpg, and only loses 1 mpg in the city to the automatic.
The question is, is the improved fuel economy worth the price premium of the four-cylinder? The automatic-only four-cylinder engine is an extra $1,000 over a V6 automatic, and $3,000 over a V6 manual. And when looking at the annual fuel cost estimates at fueleconomy.gov, you might only save $50 to $100 each year. The problem being that, while it's more efficient, it also demands premium fuel that the V6 doesn't. So it could be quite a while before the upfront cost is recouped. But if you want a Wrangler that's a little nicer to the planet, it's probably the way to go, plus you get an extra 35 pound-feet of torque over the V6, even if it means sacrificing nearly 20 horsepower.