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Jeep unveiled its new twin-turbocharged 3.0-liter inline-six engine in March 2022. The automaker said the mill would be 15 percent more efficient than comparable V8 engines, and now the EPA has official numbers to reinforce that claim. At least, that's the case when used in the flagship Grand Wagoneer SUV.

According to EPA statistics reported at fueleconomy.gov, the 2022 Grand Wagoneer with the I6 engine achieves a combined fuel mileage rating of 17 mpg. In the city, economy drops to 14 mpg but on the highway, the full-size SUV can go 20 miles on a gallon of gas. If those numbers feel a bit low for 2022, consider that the V8-powered Grand Wagoneer has a combined rating of 15 mpg, with 18 on the highway and just 13 in the city. When you do the math, the I6 does indeed offer a 15 percent improvement over the 6.4-liter Hemi.

Gallery: 2022 Jeep Grand Wagoneer: First Drive

The turbocharged six-pot is more powerful, too. Jeep lists the Grand Wagoneer as having 510 horsepower (380 kilowatts) with the 3.0-liter engine, versus 471 hp (351 kW) in the Hemi V8. Torque is considerably better with the twin-turbo engine, generating 500 pound-feet (691 Newton-meters) of twist compared to 455 lb-ft (617 Nm). Grand Wagoneer buyers will pay extra for the power and efficiency, however. The twin-turbocharged 3.0-liter engine is a $2,000 option on all four Grand Wagoneer trim levels.

For now, this new engine is only available on the Grand Wagoneer, and it's only offered with four-wheel drive. Curiously, there's an EPA listing for a two-wheel-drive Grand Wagoneer that shows slightly better city and highway mileage, with the same 17-mpg combined rating. The standard Wagoneer is available with two-wheel drive, though availability of the I6 in that model is unknown at this time. It's also unknown if Jeep will offer the full-fat 510-hp version of the engine outside the Grand Wagoneer. A detuned variant making over 400 hp (298 kW) is in the works.

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