Navistar said that it is now shipping its International DuraStar and WorkStar models with the company’s 9L and 10L engines using selective catalytic reduction emissions technology.

According to the company, the engines are producing up to an 8% fuel economy improvement over the previous generation engine.

“Our field test customers are seeing positive results – with our new trucks registering significant fuel economy improvements,” said Bill Kozek, president, North America Truck and Parts. “Our vocational trucks with 9L and 10L 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 engines bring 9.3L displacement and between 860 and 1,150 lbs.-ft. of torque in a 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.

The International DuraStar is available with the 9L engine ranging from 275 hp. and 860 lbs.-ft. of torque up to 330 hp. and 950 lbs.-ft. torque. The WorkStar is available with both 9L and 10L engines from 275 hp. and 860 lbs.-ft. of torque up to 350 hp. and 1,150 lbs.-ft. of torque.

All International vocational trucks feature the International Diamond Logic electrical system.