Ram Truck has improved the fuel efficiency of its 1500 EcoDiesel pickup with a model that edges highway fuel economy for full-size pickups closer to 30 mpg highway — a bar once thought unattainable.

The 2015 Ram 1500 EcoDiesel HFE delivers an EPA-rated 29 mpg highway, a 1 mpg improvement over the Ram 1500 EcoDiesel. Ram achieved the improvement because it "invested in powertrain technologies and those are paying real dividends," according to a release.

The 1500 EcoDiesel HFE provides 21 mpg city and 24 mpg combined.

In December, Ford's aluminum-body 2015 F-150 attained an EPA-rated 26 mpg highway when equipped with the 2.7-liter V-6 EcoBoost. The 2015 Chevrolet Silverado with the 4.3-liter V-6 has been rated at 24 mpg highway, 18 mpg city, and 20 mpg combined.

The new pickup offers a trim package to the Ram 1500 Tradesman Quad Cab four-door body with a 6-foot, 4-inch bed and 20-inch wheels. The Ram EcoDiesel also is available with a body-colored fascia adopted from the Ram Express model to give the Ram EcoDiesel HFE a sportier exterior appearance.

Wheel-to-wheel side steps and a tri-fold tonneau cover provide greater functionality and aerodynamics that improve fuel efficiency.

The EcoDiesel HFE will go on sale by April 1.