With an eye to increasing demands for fuel economy and stricter environmental regulations Cummins Inc. is launching a new line of heavy-duty truck engines.

The new diesel engines, unveiled Saturday at the Transportation Research Center’s proving ground in East Liberty, Ohio, include two 15-liter motors and a smaller 12-liter medium duty engine.

The Columbus, Ind., engine manufacturer said the new diesel engines will exceed the U.S. Environmental Protection Agency’s 2017 greenhouse and fuel efficiency standards. The EPA regulations take effect in January 2017.

The new X Series engines will also offer “lower fuel consumption, extended service intervals, enhanced performance and the highest quality standards across a 400-horsepower to 605-horsepower ratings range,” the company said in a statement.

“Many have wondered about the role of the big bore, heavy-duty engines in the North American market as compared to more recent medium-bore arrivals, begging the question whether we’ll follow what’s been happening in Europe,” said Lori Thompson, vice president of marketing for Cummins. “With the benefit of several years of market experience, we can answer that question – the big bore engine is here to stay.”

The new 2017 engines will offer a 3 percent fuel economy improvement over its 2016 engines, said Mario Sanchez, Cummins’ spokesman.

The X series offers two new heavy-duty engines designed for fleets and the owner-operator market, while Cummins’ previous ISX platform only offered one 15-liter engine.

“Each one (engine) is optimized to meet the demands of our customers with vastly different trucking applications,” said Tim Fier, vice president of engineering for Cummins’ engine business.

The X15 Performance Series is designed for heavy-haul and vocational trucks, with a 485-horsepower to 605-horsepower range. The engine offers peak torque ratings up to 2,050 pounds per feet and engine braking up to 600 horsepower.

The X15 Efficiency Series is designed for line-haul and regional-haul applications with a 400-horsepower to 500-horsepower range. The engine offers peak torque ratings of up to 1,850 pounds per feet.

“Our latest X15 and X12 engines deliver unparalleled performance while achieving the lowest cost of operation,” said Srikanth Padmanabhan, president of Cummins’ Engine Business.

Its new X12-liter medium bore engine is designed for regional-haul, city and vocational applications with up to a 475-horsepower range and up to 1,750 pounds per feet of torque. The new engine is 150 pounds lighter than its closest competitor, Thompson said.

Full production of the X12 series is expected to start in 2018.

All three of the new engines will be built at Cummins’ Jamestown Engine Plant in Jamestown, New York.