2018 Ford F-150 Power Stroke Diesel rated at 30 mpg highway, with a big catch

A new turbodiesel V-6 gives the rear-wheel drive 2018 Ford F-150 Power Stroke Diesel fuel economy akin to a mid-size sedan, but the four-wheel drive version is much thirstier.

Ford said Thursday that the EPA rates the rear-wheel-drive diesel pickup at: 22 mpg city, 30 highway, 25 combined. The four-wheel drive one comes in at just 20/25/22 mpg, a figure on par with most gas-fueled pickups and not far off of the 18/25/21 mpg rating of the most powerful engine available in the F-150, the 3.5-liter twin-turbo V-6.

That 30 mpg figure is enough to make the rear-drive F-150 a teetotaler among half-ton pickups, however. Its next-closest rival is the 2018 Ram 1500 EcoDiesel, which is rated by the EPA at 20/27/23 mpg with rear-wheel drive. The Ram with four-wheel drive and the diesel is rated at 19/27/22 mpg.

MORE: Read our 2018 Ford F-150 review

It's not clear how long Ford will hold the most fuel-efficient claim, however. The redesigned 2019 Ram 1500 will offer a diesel V-6, though the truckmaker hasn't detailed that engine yet. Additionally, its standard gas V-6 will come with 48-volt mild-hybrid technology designed to reduce fuel consumption, too—but, again, EPA figures haven't been released.

The F-150's 3.0-liter turbodiesel V-6 produces 250 horsepower and 440 pound-feet of torque, and Ford says that's good for a tow rating of up to 11,400 pounds when properly equipped. Curiously, that's nearly 2,000 pounds shy of the maximum trailer rating for a properly-equipped gas-engined F-150.

Additionally, Ford says that fleet versions of its F-150 Power Stroke Diesel have a 2,020-pound payload capacity, which shrinks to a still decent 1,940 pounds for versions offered to retail customers.

DON'T MISS: Ford's 3.0-liter turbodiesel V-6 explained

Ford expects just 5 percent of F-150 buyers to opt for the turbodiesel V-6, which joins four gasoline engines ranging from a 3.3-liter V-6 to a twin-turbo 3.5-liter V-6. Fleet buyers will be able to order the F-150 Power Stroke Diesel in XL and XLT trim levels, while retail shoppers will have to stick with Lariat, King Ranch, and Limited trims.

It won't come cheaply, either. On the 2018 F-150, the turbodiesel V-6 is being positioned as the range-topping engine, and it is saddled with a premium of as much to $4,000 depending on the trim level.