“Natural Gas Vehicles The Clean Way to Go with a Domestic Fuel”. Washington Gas.: Natural gas is the cleanest-burning fossil fuel available. Natural gas vehicles can achieve up to a 93 percent reduction in carbon monoxide emissions, 33 percent reduction in nitrogen oxides emissions, and a 50 percent reduction in reactive hydrocarbons in comparison with gasoline vehicles. Natural gas vehicles emit virtually no carcinogenic particulate matter. In addition, because natural gas burns cleanly, maintenance costs are low. Natural gas extends the time needed between tune-ups and oil changes, and results in less engine wear-and-tear. Also, natural gas has an octane rating of 130, which means it has an efficiency advantage over gasoline.