What is the difference between CNG and LPG?
CNG is Compressed Natural Gas. This is a gaseous fuel compressed under very high pressure. The normal tank pressure in a CNG system is 3600 P.S.I. When used as a motor fuel this pressure must be reduced first from 3600 P.S.I. to 150 P.S.I., then from 150 P.S.I. it is reduced to a low positive pressure. LPG is Liquefied Petroleum Gas. As the name implies it is petroleum based. This is a liquid fuel that is stored at 150 P.S.I. The liquid fuel is heated to vaporize it and is reduced from 150 P.S.I. to negative pressure. Negative pressure means that the vacuum from the engine draws the fuel from the secondary regulator as needed. Both fuels will give less mileage than gasoline. LPG is usually 10% less mileage and CNG 15% less. This is due to the lower BTU rating of these two fuels compared to gasoline.
