Natural gas still hasn't really caught on as a fuel for private passenger vehicles, but it's slowly finding more success in commercial applications.
The selection of natural-gas commercial vehicles is much larger, and using the fuel in fleets makes more sense from an environmental-impact standpoint than it does for individual cars.
One company catering to this market is Mack Trucks, which announced that the natural-gas versions of its Pinnacle series trucks will get a handful of updates this year.
These include a new Eaton UltraShift Plus automated transmission and Wingman Advanced safety system.
Mack Pinnacle series
The latter is essentially an adaptive cruise control system--commonplace in cars, but fairly new to big trucks--that can automatically keep a set following distance by reducing throttle or engaging the engine retarder and brakes.
All natural-gas Mack Pinnacle models use a Cummins Westport ISX12 G engine that can run on either compressed natural gas (CNG) or liquefied natural gas (LNG).
The two fuels are somewhat different. LNG's liquid state is denser and makes it easier to transport, but CNG is generally cheaper, more widely available, and doesn't need to be kept at low temperature like LNG.
Sales of natural-gas trucks have risen lately, but the economics of the trucking industry still keep them from being widely adopted.
Clean Energy Fuels natural gas refueling station Long Beach, California.
While natural gas is typically much cheaper than diesels, the trucks themselves are more expensive to start out with--sometimes by as much as a third over a comparable diesel-powered semi tractor.
Mack claims cheap fuel lowers the lifetime costs of a natural-gas truck, but the relatively quick turnover time of equipment in fleets means the initial buyers often don't see these savings.
Customers also expect fleet operators to pass on cost savings in the form of lower rates, cutting any potential benefit from natural gas.
In addition, there still aren't many public natural-gas fueling stations in the U.S.--and even fewer that can accommodate large trucks.
[EDITOR'S NOTE: Green Car Reports thanks our tipster, who prefers to remain an International Man of Mystery.]