General Motors will begin taking customer orders this spring for heavy-duty models of its Chevrolet Silverado and GMC Sierra large pickup trucks fueled by an industry-first combination of compressed-natural gas and regular gasoline.

The auto maker expects deliveries of the pickups from its Fort Wayne, IN, assembly plant to start later in the year.

GM does not release fuel-economy estimates or pricing. But the auto maker says the bi-fuel pickups, both of which use a 6.0L V-8 engine, will have a range of 650 miles (1,046 km) from their 17-gallon (64L) CNG and 36-gallon (136L) gasoline tanks.

The U.S. government does not require fuel-economy estimates in the heavy-duty Silverado and Sierra’s weight class, making comparisons with gasoline-only models difficult.

However, a 4-wheel-drive Silverado 1500 with a 34-gallon (129L) gas tank gets a combined-cycle 17 mpg (13.8 L/100 km), according to the Environmental Protection Agency, giving it an estimated range of 612 miles (985 km).

GM expects commercial buyers to gravitate to its new bi-fuel pickups more than retail customers, given the trucks likely will come at a premium price. Plus, the CNG fueling infrastructure remains uneven and mostly is found in pockets, such as in Southern California, New York, Oklahoma and Utah.

Last year, GM began volume sales of its Chevy Express and GMC Savanna large vans to commercial customers that use CNG fuel exclusively.

Joyce Mattman, director-GM Commercial Product and Specialty Vehicles, says owners of GM CNG vans report lower operating costs. CNG costs between $2.15 and $2.25 a gallon, while gasoline prices are again approaching $4 per gallon.

CNG prices also are not linked to wildly fluctuating oil prices, giving the fuel pricing certainty. However, range is limited and the under-developed CNG fueling infrastructure presents “challenges,” she says.

“That’s why we felt the bi-fuel (pickups) would have broader appeal,” Mattman tells journalists in a conference call ahead of the GM trucks’ debut at Tuesday’s NTEA Work Truck show in Indianapolis, IN.

After the Silverado and Sierra pickups are built in Fort Wayne, one of two GM facilities that produce its HD models, Tier I supplier IMPCO Technologies will add the CNG systems.

The bi-fuel trucks will be covered by GM’s standard 3-year, 36,000-mile (57,935-km) limited warranty and 5-year 100,000-mile (160,930-km) powertrain warranty. All sales and service will be conducted at Chevy and GMC dealerships.

“This is part of the GM manufacturing process, not an aftermarket installation,” Mattman tells WardsAuto. “Our engineers are there making sure every single aspect of the manufacturing process happening at our plant and our Tier I suppliers absolutely meets GM requirements.”

The auto maker says it is planning to conduct a number of crash tests to ensure the durability of the fuel tanks.

The auto maker got into a flap last year when a government crash test of the Chevy Volt extended-range electric vehicle caused the car’s battery pack to catch fire.

None of GM’s severe crash testing of the Volt revealed the potential for a fire, and no real-world fires have occurred. The car since has been deemed safe, but it continues to suffer from the public’s perception.

GM’s bi-fuel pickups borrow the Volt’s propulsions strategy by combining an alternative fuel, CNG, with a range-extending internal-combustion engine. The Volt uses a battery for electric propulsion and a small ICE to extend its range.

Mattman says GM used it global expertise in CNG-powered vehicles to design the bi-fuel pickups.

The bi-fuel Silverado and Sierra HDs will be available in both 2-wheel and 4-wheel drive and short- and long-box configurations with an extended cab.

jamend@wardsauto.com