The new 2018 Wrangler is a big deal for Jeep, and in its redesign the company didn't leave its fuel economy stuck in the mud.

In addition to the fuel-swilling V-6, the new Wrangler will be available with a more efficient turbocharged 4-cylinder engine, and the EPA has just revealed exactly how efficient it will be.

The two-door turbo-4 sits atop the figurative Wrangler mountain lineup with ratings of 23 mpg city, 25 highway, 24 combined. Should you need four doors, those numbers drop to 22/24/22 mpg.

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The numbers represent a significant improvement in a popular vehicle that shares its aerodynamic properties with a school bus. If regulators and automakers are serious about cleaning up the air and reducing carbon dioxide emissions, these are the types of vehicles that need improvement the most, and where the biggest savings are available.

There's more. What Jeep won't be advertising is that turbo-4 powertrain is actually a mild hybrid with a 48-volt electrical system replacing the alternator with a motor-generator. This setup shuts down the Wrangler's gas engine while coasting and at a complete stop. The former is referred to as "sailing."

The improvement in the four-door Wrangler's fuel economy numbers represent a significant 22-percent reduction in fuel consumption in mixed driving compared with last year's model, which only came with a V-6.

The Wrangler is one of Jeep's best sellers. Last year the automaker moved 190,522 of them. Fully 80 percent were four-doors, most of which had automatic transmissions and EPA ratings of 16/20/18 mpg.

2018 Jeep Wrangler Rubicon

2018 Jeep Wrangler Rubicon

Assuming for argument's sake that all were four-doors, and that they were each driven 14,500 miles a year (the national average for new cars), the new Wrangler four-door with its turbo-4 could save almost 28 million gallons of gas a year. All that fuel not burned is also not turning into either smog or carbon dioxide.

The 4-cylinder Wrangler two-door's 23-mpg city figure is significantly better than the V-6's 18 mpg with an automatic and 17 mpg with a 6-speed manual transmission.

2018 Jeep Wrangler

2018 Jeep Wrangler

While V-6 buyers can still get a stick shift, those who opt for the turbo-4 will have no choice but the 8-speed automatic transmission, which actually improves fuel economy with the V-6. We'll have to see how it pairs with the turbo-4 in the real world.

The turbo-4 is rated at 270 horsepower and 295 pound-feet of torque, with the latter coming on in full at just 3,000 rpm.

For those who want even better fuel economy as well as more torque, there will be a diesel engine coming in 2019. The most fuel-efficient Wrangler likely will be the plug-in hybrid model, which is set to go into production in 2020.

All of this—the mild-hybrid 48-volt electrical system and plug-in hybrid model—is part of Fiat Chrysler Automobile's broader push for fuel-efficiency gains. Today the automaker already has the plug-in Chrysler Pacifica Hybrid (Green Car Reports' Best Car To Buy 2018) and the new 2018 Ram 1500 will only be available as a hybrid (featuring the Wrangler's 48-volt electrical system) in V-6 form (V-8 buyers can opt out of the hybrid setup).

The turbo-4-powered Wranglers will hit dealerships in the summer of 2018, and the engine carries a $1,000 premium regardless of which Wrangler trim or model it's in.