Low reactivity. Propane exhaust creates 60-70 percent less smog than the hydrocarbons in gasoline exhaust, according to studies by Southwest Research Institute.

Low air toxics. Propane cuts emissions of toxins and carcinogens like benzene and toluene by up to 96 percent, compared to gasoline, according to studies by Southwest Research Institute.

Ground- and surface-water safe. Propane is nontoxic; spills vaporize rather than soaking into soil or water.

Low greenhouse-gas emissions. Propane has the best greenhouse-gas emissions performance of any fossil transportation fuel when emissions from the complete fuel cycle of production, distribution and combustion are considered. Propane offers substantial greenhouse benefits compared to gasoline in light-duty vehicles and diesel fuel in heavy-duty vehicles.

An analysis by M. A. DeLucchi for Argonne National Laboratory concluded that the LPG fuel cycle produces the least amount of greenhouse gases of all the fossil fuel cycles, including that of diesel fuel. The study concluded that “Liquefied petroleum gas, consisting of 95% propane and 5% butane, offers a 20-25% reduction in emissions of greenhouse gas from LDVs [light-duty vehicles] (compared with gasoline). Moreover, the use of LPG in HDVs [heavy-duty vehicles] would actually decrease greenhouse gas emissions (compared with diesel fuel). The combined HDV-plus-LDV effect of an LPG policy would be a better-than-15% reduction in fuel cycle emissions of greenhouse gases.”