LOUISVILLE, KY -- Navistar International's new MaxxForce 15 diesel, first will reside in a longer version of the ProStar+ aerodynamic tractor, the company announced on the eve of the opening of the 2011 Mid-America Trucking Show.

The 15-liter engine, unveiled last week at the ConExpo construction show in Las Vegas, will also be offered in International 5900 severe-service trucks and tractors. For them the MaxxForce 15 will be rated up to 550 horsepower; for the ProStar+ highway tractor, ratings will go to 500 hp.

The MaxxForce 15 combines Navistar air, fuel and electronic control systems with a block, head, crankshaft, and connecting rods from Caterpillar's rugged C15 engine, said Jim Hebe, senior vice president for North American sales operations.

The latest version of the International ProStar+ will have a longer nose to accommodate the large MaxxForce 15, and a bumper-to-back-of-cab dimension of 125 inches. It joins the 115- and 122-inch-BBC versions of the tractor that use Navistar's MaxxForce 11 and 13 diesels.

The 15-liter is needed by customers whose demanding applications require more displacement, power and torque, Hebe said in explaining the big-bore engine's development. Use of parts from Cat, Navistar's truck partner here and overseas, allowed complete design and testing in an "unheard of" two years, Hebe said, because "engineers were fine-tuning existing components."

But the MaxxForce 13 is still able to do most assignments seen in the on-highway truck world, Hebe said. Its ratings of up to 475 horsepower and 1,650 pounds-feet "hit the sweet spot" of customer demand, and more fleet buyers are adopting this engine. A new rating of 500 horsepower and 1,700 pounds-feet will make it more capable.

The MaxxForce 15 is the seventh Navistar engine and gives the company "the most complete lineup of engines in the trucking industry," Hebe said. The products include the MaxxForce 7, DT, 9, 10, 11 and 13. They are the only engines now available in International's medium- and heavy duty trucks.

Navistar is also working on alternative fuel products, and is showing a dual-fuel MaxxForce 13 engine in a ProStar+ 122-BBC tractor at Louisville, Hebe noted. The natural gas-diesel engine was developed with Clean Air Power Ltd., which has operations in the United Kingdom and Australia.

The tractor has a liquefied natural gas fuel system with a 119-gallon cryogenic storage tank, a coolant-heated fuel vaporizer, and an LNG regulator and filter. It burns an 85-15 mixture of natural gas and diesel, and develops 430 hp and 1,550 lbs-ft.

Navistar has delivered on all of its promises for high-performing products made in recent years, Hebe declared. And executives have decided to put aside the bickering over which system, Navistar's Advanced Exhaust Gas Recirculation or competitors' selective catalytic reduction, does a better job of controlling nitrous oxide pollutants.

Instead, Navistar will concentrate on its advantages in trucks, engines, fuel economy, and its widespread dealer support. And Hebe announced incentives for two options. A customer can take $3,500 off the price of Eaton's UltraShift Plus automated mechanical transmission or choose the no-cost addition of Meritor Wabco's OnGuard collision avoidance system.

International dealers have details on new and current products, and potential buyers meanwhile can get information at www.navistar.com.