A full-sized pickup that can get 30 mpg sounds impressive, and it is. Ford has released the fuel economy ratings for the new F150 Powerstroke diesel, and that's the highway rating for the two-wheel drive model.

In the city it's rated to get 22 mpg from its turbocharged 3.0-liter V6 engine, and gets a combined rating of 25 mpg in mixed driving.

If you need a pickup, and want to save as much gas as possible, the F-150 diesel can do that for you.

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

Four-wheel drive models, though, you take a big hit. They are rated to get 25 mpg on the highway, 20 in town, and 22 overall.

We dug a little deeper into the numbers, though, and found that the F-150 diesel may be a hard sell.

The engine option adds about $4,000 over the price of the 2.7-liter EcoBoost V6, depending on the trim level.

Compared with the 3.5-liter EcoBoost V6, which gets the F-150's highest tow rating, the diesel costs $2,400 more.

2018 Ford F-150 Power Stroke

2018 Ford F-150 Power Stroke

With four-wheel drive, the 2.7-liter is rated at 19 mpg city, 24 highway, and 21 mpg overall, just one mpg short of the diesel. The 3.5 is rated at 17 city/23 highway/19 mpg overall. 

So the F150 with two-wheel drive gets near car-like mileage on the highway, but the 2.7-liter EcoBoost does almost as well for a lot less money. With four-wheel drive, the difference is even starker.

Some pickup buyers look to diesel trucks for big towing capacity, and the F-150 diesel's 11,400 pounds is an impressive number—but it's about 2,000 pounds short of the highest-rated F-150 with a gas engine.

CHECK OUT: Under pressure: Ford F-150 diesel aims for big towers, bigger cruising distances

Saving gas is arguably more important in pickups than it is in cars, both because they burn so much of it and because pickups are so popular with American buyers that any gains are magnified relative to cars.

That's a big reason why all of the American automakers are focusing on improving fuel economy in their full-sized pickups. Ram will also get a new 3.0-liter V6 turbodiesel for 2019, along with a 48-volt mild hybrid system to reduce idling in the city to save gas. General Motors also announced a new six-cylinder diesel for its Chevrolet Silverado and GMC Sierra pickups.

All these efforts are worthwhile. We just hope they prove compelling for consumers when they head to the showroom. If few buyers are willing to pay the premium, these new technologies won't save much gas on the road.