CNG stands for Compressed Natural Gas. It is gaseous fuel and is a mixture of hydrocarbons mainly Methane. For use in Automobiles as fuel substitute for other auto fuels such as petrol, diesel, Auto LPG etc, it is compressed to a pressure of 200-250 Kg/cm² to enhance the vehicle on-board storage capacity.
Commonly referred to as the green fuel because of its lead and sulphur free character, CNG reduces harmful emissions. Being non-corrosive, it enhances the longevity of spark plugs. Due to the absence of any lead or benzene content in CNG, the lead fouling of spark plugs, and lead or benzene pollution are eliminated.
Another practical advantage observed is the increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil.
CNG is less likely to auto-ignite on hot surfaces, since it has a high auto-ignition temperature (540 degrees centigrade) and a narrow range (5%-15%) of in flammability. It means that if CNG concentration in the air is below 5% or above 15%, it will not burn. This high auto ignition temperature and narrow flammability range makes CNG as safer fuel.
The operational cost of vehicles running on CNG, as compared to those running on other fuels, is comparatively low.