Hribar Logistics of Caledonia, Wis., added two Kenworth 440 compressed-natural-gas tractors to its fleet powered by the Cummins Westport ISL G.

Hribar Logistics, a full-service trucking and logistics provider, hauls general freight and dry-bulk materials and aggregates. Its 60-truck fleet consists primarily of Kenworths.

"We embraced the idea of using CNG because it costs less than diesel and helps to increase our country's energy independence," said Mark Hribar, director of fleet operations for Hribar. The average nationwide price of an energy-equivalent amount of CNG recently was $1.47 less than a gallon of diesel fuel, according to the July 2011 Clean Cities Alternative Fuel Price Report from the U.S. Department of Energy.

The two CNG-powered Kenworth T440s are dedicated to an earmarked transportation lane in order to track and compare their performance against documented history of similar Hribar trucks using diesel fuel.

The T440s' ISL G engine uses a maintenance-free, three-way catalyst and is 2010 EPA- and CARB-compliant without the use of selective catalytic reduction technology or a diesel particulate filter. Rated at 320 horsepower and 1,000 pounds-feet of torque, the engine's torque curve closely matches that of its diesel counterparts.

The truck uses an Allison 6-speed transmission. The Kenworth T440s come equipped with the Kenworth QuietCab package, 12,000-pound rated taperleaf spring front suspension and Kenworth AG400L air-ride rear suspension rated at 40,000 pounds.

The Wisconsin Clean Transportation Program, administered jointly by the Wisconsin Office of Energy Independence and the Wisconsin Clean Cities-Southeast Area, helped provide funding through a federal grant for the additional up-front cost of the CNG technology.