Navistar Inc. has started customer shipments of its first International DuraStar and International WorkStar vehicles with the company’s 9- and 10-liter engines with selective catalytic reduction (SCR) emissions technology. According to the company’s internal testing, these products deliver up to an 8% improvement in fuel economy over the previous generation.

“Our field test customers are seeing positive results, with our new trucks registering significant fuel economy improvements,” said Bill Kozek, president of North America Truck and Parts, Navistar. “Our vocational trucks with 9- and 10-liter engines are also experiencing fewer active regenerations while still delivering the durability and power that customers expect from International trucks.”

Built on Navistar’s I-6 platform, the company’s 9- and 10-liter engines bring 9.3-liter displacement and 860-1,150 lb.-ft. torque in a weight-saving medium-duty package. The company conducted field tests in extreme environments such as Alaska, Colorado and Arizona. These tests included a variety of vocational duty cycles from garbage packing and utility trucks to dump trucks and sewer pumpers.

“We’ve run our DuraStar with the 9-liter for around 40,000 miles during the last two months,” said Robbie Easley, owner of Easley Trucking. “We haul mail and the 9-liter has performed well on the steep hills our trucks climb daily. This truck runs between Phoenix and Yuma, Ariz., one of the hottest environments you can find, and it hasn’t missed a beat.”

The International DuraStar is available with the 9-liter engine from 275 hp 860 lb.-ft torque up to 330 HP 950 lb.-ft torque. The International WorkStar is available with 9- and 10-liter engines from 275 HP 860 lb.-ft torque up to 350 HP 1,150 lb.-ft torque.