Pickup-truck buyers are notoriously demanding and brand-loyal, especially when it comes to heavy-duty pickups used for work to haul heavy equipment and for recreation to tow campers, boats and horses.

This year, that segment is flush with fresh product as General Motors Co. and Ford Motor Co. launch all-new versions of their Chevy Silverado/GMC Sierra HD and Ford Super Duty pickups, respectively. And Chrysler Group LLC refreshed its Ram heavy-duty trucks late last year.

All three offer astoundingly powerful turbodiesel engines, and Ward’s Automotive Group is setting out to pick the best of the three at a “Diesel Shootout” to be held this week at Robert Bosch LLC’s test track in Flat Rock, MI.

Editors at Ward’s and Fleet Owner magazine, a fellow Penton Media Inc. publication for commercial-trucking companies, will drive Detroit’s three HD diesel pickups, each towing 10,000 lbs. (4,536 kg) on the 1.3-mile (2-km) oval at the Bosch track and on a 20% grade.

Following the template of the annual Ward’s 10 Best Engines competition, editors will score each engine based on acceleration, technology, fuel efficiency, driveability and overall power, paying close attention to noise, vibration and harshness levels at idle, cruising speed and during hard acceleration.

Points also will be awarded based on observed fuel economy and the application of new technology. Gasoline V-8s in big pickups guzzle fuel, but modern common-rail diesels generally are about 25% more efficient, while producing staggering amounts of torque.

The newest diesels are GM’s 6.6L Duramax V-8 and Ford’s 6.7L Power Stroke V-8, which produce 765 lb.-ft. (1,037 Nm) and 735 lb.-ft. (997 Nm) of torque, respectively, at 1,600 rpm. Carried over for the new-for-’10 Ram HD is the stout 6.7L Cummins Inc. inline-6, capable of 650 lb.-ft. of torque (881 Nm) @1,500 rpm.

To keep a level playing field, all three trucks for the “Diesel Shootout” will be roughly the same: three-quarter-ton 4x4 turbodiesel crew cabs with automatic transmissions and axle ratios of about 3.73.

After the track driving, the event will move to the open road, where trailers will be towed at steady speeds on surface streets and highways. Tens of thousands of these trucks are used every day in the U.S. in such a way.

In past years, heavy-duty pickups were part of the Ward’s 10 Best Engines competition, which places a heavy emphasis on real-world driving in every-day commutes, and all three Detroit auto makers have earned Best Engines awards for their heavy-duty diesels.

But those awards were given without evaluating the trucks as they were intended to be used: towing trailers with big loads.

The “Diesel Shootout,” conceived with the help of fuel-injector and engine-control supplier Bosch, is a new tool that enables real-world truck evaluation.

Ward’s will announce the winner of the event in September, and the trophy will be presented at the 2011 10 Best Engines banquet, to be held Jan. 12 during the North American International Auto Show in Detroit.

tmurphy@wardsauto.com