Natural gas has been used in lieu of gasoline or diesel in a small number of vehicles worldwide for decades. American car makers are starting to embrace its use, as General Motors and Chrysler have both announced natural gas pickup models by the end of the year.

Lower emissions

Natural gas, a hydrocarbon gas composed mostly of methane, is usable in vehicles when either compressed or liquified, at which point it is referred to as either Compressed Natural Gas, or CNG, or Liquified Natural Gas, or LNG, according to the Department of Energy, CNG being the most common.

CNG has a lower energy content than gasoline but produces fewer emissions. CNG vehicles achieve comparable performance and efficiency to gasoline vehicles, though some are optimized to use both gasoline and natural gas, called bi-fuel vehicles. Two of Detroit’s Big Three are planning to launch bi-fuel pickups by year’s end, according to the Wall Street Journal.

Here by fall

Chrysler, according to the Wall Street Journal, is going to install the CNG system on at least 2,000 Ram 2500 pickups, beginning in June. Chrysler is getting the technology from its parent, Fiat, which has been making bi-fuel cars for some time already. The trucks are intended for fleet sales.

General Motors, according to USA Today, is launching bi-fuel versions of the 2013 Chevrolet Silverado and GMC Sierra 2500 HD extended-cab trucks, which will start production in the fourth quarter.

GM previously made a limited run of CNG cars along with Ford in the 1990s that weren’t successful and CNG versions of the Chevrolet Express and GMC Savana cargo vans have been available for some time for fleet use, according to AutoBlog. Ford, according to the Wall Street Journal, already offers CNG conversion kits for select vehicles.

Range extending gas tank

Both trucks will have CNG fuel tanks mounted in the bed, along with a gasoline tank. Chrysler, according to the Wall Street Journal, estimates the CNG Ram will have a range 255 miles on CNG before switching to gasoline, which should extend the range a farther 112 miles. GM estimates a 650-mile range for the CNG Sierra and Silverado. GM says transitioning the 6-liter Vortec V-8 between gas and CNG is “seamless.”

The only CNG vehicle currently available as a passenger car is the Honda Civic Natural Gas, formerly the GX. According to the Boston Globe, it’s a Civic EX that has been converted to use CNG, though it costs $5,600 more than its gas counterpart. It gets only 1 mpg less than the gas model but loses 30 horsepower because of the lower energy content of CNG.

[Test drive a Civic Natural Gas at Howdy Honda, the go-to source for Hondas]

That said, according to the Department of Energy, it has a lower operating cost because natural gas costs about five-eighths as much as gasoline. The Civic NG also produces 54 fewer grams of carbon dioxide per mile than the gas model.