Derric Dial, a mechanic at Semi Services, left, and Michael

UNITED STATES - MAY 23: Derric Dial, a mechanic at Semi Services, left, and Michael Fitzgerald, owner of Semi Services, maneuver a natural gas storage tank into the bed of a 2008 Chevy Silverado LTV pickup truck during its conversion to natural gas power in Salt Lake City, Utah, U.S., on Friday, May 23, 2008. Natural-gas autos, sold by many carmakers in the 1980s and 90s, fell from favor in the past decade because of federal fuel-economy credits for less-costly ethanol-powered models, a drop in gasoline prices and the volatile cost of natural gas. The Honda Civic GX is currently the only natural-gas model still sold directly to consumers by a major auto manufacturer, and John Mendel, executive vice president of U.S. sales for Honda, said in February that sales could rise 10 times the current level of about 1,000 a year in the United States. (Photo by George Frey/Bloomberg via Getty Images)