Engineers at Cummins have retuned their-heavy duty ISX11.9 diesel for better performance and fuel economy, and marketers have stepped up promotion of the engine by renaming it the ISX12.

Recalibrating the engine's controls has resulted in fuel economy betterments of up to 5% in road tractors and as much as 12% in vocational applications, the company said. The calibration work is electronic and the engine is physically the same as when it was introduced for 2010.

The new rounded-up numerical designation is in line with those for Cummins' other heavy-duty truck engine products, like the ISL9 and ISX15, and is easier to read and say than the old 11.9 name, representatives said.

In Cummins' lineup chronology, the ISX11.9 replaced the similarly sized ISM that had succeeded the L10. The ISX12 continues to fill that role in engine size, but its design is based on the big-bore ISX15.

The ISX12 has on-highway ratings from 310 horsepower and 1,150 pounds-feet to 425 horsepower and 1,650 pounds-feet, plus variable Smart Torque ratings of 1,250-1,350 to 1,450-1,650 pounds-feet Vocational ratings start at 320 horsepower and go to 425, with torque outputs of 1,150 to 1,650 pounds-feet.

Torque output at clutch engagement is a strong 800 pounds-feet, making the ISX12 an excellent engine for refuse, construction and other vocational applications, the company said. Integrated rear- and front-engine power take-off drives are available.

More information is available at Cummins dealers, at or by calling 1-800-DIESELS (1-800-343-7357).