I’m driving a humongous Ford F-250 that runs on exactly the same stuff that powers your gas grill. You’ve probably never given much thought to propane, but it’s a cool fuel, and not just for wiener roasts. We could convert a lot of our fleet to clean-burning propane, and it’s domestic to boot. There are 17 million vehicles burning propane autogas on the world’s roads now, but just 350,000 in the U.S., including a lot of school buses and (in the South mostly) police cars. It's kind of under-the-radar technology, though the Propane Education and Research Council (PERC) (headed by the very enthusiastic Roy Willis) is pretty vocal.

My truck has a big white 100-gallon tank in the bed, which is easily enough to give me 600-mile range. I get to pass gas stations, though when I finally do need fuel, it’s a 10-minute process. It takes longer than getting gasoline, not as long as charging an electric car. It’s dead easy, and it’s certainly a treat to be paying about $2 or $2.25 a gallon. The great advantage of this fuel is that it's a liquid at near-room temperature. It's not quite as convenient or as packed with energy as gasoline, but it's not so far off.

Propane has less energy content than gasoline (5 to 10 percent by volume), so it’s not a straight comparison to today’s pump fuel, but you won’t notice much difference from the driver’s seat. I squired the big 5.4-liter V-8 Ford around all over town and didn’t lack for power. It will haul as much as the gasoline version (though that propane tank takes up some space).

America has untold riches in natural gas, thanks to hydraulic fracturing. Yes, there are big downsides to that practice, but upsides, too — possible energy independence for the U.S. in a few years, a return of some forms of manufacturing, and a practical alternative to gasoline for fleet transportation. Cheap propane is a welcome byproduct of all that natural gas we've recently discovered.

I’m in Norwalk, Conn., visiting a filling station (pictured at right) with David Gable, president of Hocon Propane, and Joe Rose, president of the Propane Gas Association of New England. Gas has a big price advantage over fuel oil these days, so Hocon’s main business is providing propane for heat, hot water and cooking. Its trucks run on propane, too, and it was Rose’s New Hampshire-based work truck that they let me borrow for a week.

“Your local propane dealer, the guy with the 1,000-gallon tank who fills up your grill cylinders, can easily adapt to fueling vehicles,” Gable says. “All you need is some kind of meter so you can accurately track fuel sales [propane for trucks is taxed; propane for cooking is not], and a beefier pump so you can fill faster.” Unlike CNG, propane has minimal compression, so the equipment is relatively cheap.

A key question here is whether adequate propane supplies exist to significantly ramp the stuff up as a transportation fuel. There’s certainly no widespread agreement on that. Dave Demers, the CEO of Westport, is skeptical about propane’s potential. Westport converts the same F-250 trucks to CNG in partnership with Ford. 

In an interview at New York’s Oyster Bar, he said the current volume of propane is inadequate for rapid expansion, and that commercially available propane varies widely in quality. (That’s true, though the propane autogas in my tank is a more consistent product than gas grill fuel.) “Everybody is talking about what the next alternative fuel will be, and I think it’s CNG rather than propane,” he said. Demers (pictured below) likes propane for forklifts and other applications.

CNG isn’t standing still. The industry (with around 500 U.S. public stations) is poised to introduce new low-cost home fillers that could lead to more natural gas cars on the market. (Right now, there’s only the Honda Civic in the U.S.) Demers also says that Westport is working on low-emission direct-injection systems that will allow dual-fuel CNG-gasoline vehicles that rely on one set of injectors and rails. “Dual fuel should eliminate range anxiety,” he said.

Others in the CNG industry are more sanguine about propane. Jim Arthurs, president of the Cummins-Westport joint venture, says that the company sold propane conversions from the late 1990s until 2009, but discontinued them due to lack of interest. Now, he says, propane is more widely available and very reasonably priced as part of the fracking phenomenon, and the school bus market is heating up. “We’ll keep an eye on the trends, “Arthurs said.

David Gable says there’s no problem sourcing propane today. “We’re net exporters,” he said. There does seem to be a lot of it around. More than 8 million households use it as fuel, about half of those as the main heating source. The gas grill market (using small tanks like those arrayed around the 1,000-gallon tank at left) is also huge. Ninety percent of our propane is domestically produced, 70 percent as a byproduct of natural gas and 30 percent from oil refining. We have 25,000 retail outlets selling propane, plus 70,000 miles of cross-country pipeline and 25,000 trucks for moving the fuel.

So far, propane transportation is growing in pockets. It’s easy to set up a refilling station for small fleets, so those Southern sheriffs have been using confiscated drug money to pay for conversions and infrastructure. Other strongholds include the western U.S. and Canada.

Trucks can be converted to bi-fuel operation, gasoline and propane, for $6,000 and up. Michigan-based Roush CleanTech offers a propane-only conversion of the Ford F-250 for about $10,000. Add that amount again for a modest propane fleet refueling station with meter and pump. It’s not a huge outlay. Here's a visit to the propane filling station, on video:

“From the industry’s perspective, propane conversions aren’t an option for car owners, but they do make sense for fleets,” says Joe Rose. “We see a big market early on in the conversion of existing trucks.”

I’m back on the road in my propane F-250. In the rear-view mirror, I can see that 100-gallon tank in the truck’s bed. It’s a comforting sight, because with a big tank I have big range, and I can wave as I go past all those $3.89 a gallon signs on the highway. Did I mention that propane costs about half that?

Jim Motavalli ( @jmotavalli ) writes about cars, technology and the environmental world to anyone curious enough to ask.