While the enormous torque of the 2020 Jeep Wrangler EcoDiesel is one particularly appealing aspect of the powertrain, the promise has been that the diesel Jeep would be significantly more fuel efficient than other Wranglers. That promise has been fulfilled now that official EPA numbers show it returns 29 mpg on the highway, 22 in the city, and 25 in combined driving. Those numbers are for the four-door model with an automatic, since that's the only configuration available with the diesel V6.
In comparison, the next most efficient Wrangler is a two-door model with the four-cylinder gas engine and an automatic, with 24 mpg on the highway, 22 in town, and 23 in combined driving. Behind that is the four-door with the same powertrain, which returns 22 on the highway, 21 in town and 21 combined. A manual transmission two-door Wrangler with the gas V6 actually manages 25 mpg on the highway, higher than the four-cylinder two-door variant, but its city and combined ratings are lower than the four-cylinder Wranglers.
In fact, the diesel Wrangler even performs slightly better than the Ram 1500 EcoDiesel when it has four-wheel drive, beating the full-size truck by 1 mpg in town and in combined driving. Of course the two-wheel-drive Ram outperforms both of them.
The diesel may not be the way to go for saving money, though, unless you're spending a large amount of time on the highway. Because of the extra cost of diesel fuel, the EPA estimates the annual fuel cost of the diesel to be $1,850, which is $250 more per year than the two-door four-cylinder Wrangler, and $50 more per year than the four-door four-cylinder version. The V6 Wranglers have annual fuel costs a bit higher, between $1,900 and $2,000. You're not just paying for the fuel either, since the diesel engine is a $4,000 option. But if you want lots of torque, fewer finite resources used, and fewer carbon dioxide emissions, the diesel is still a compelling option.