The right value for LPG can be obtained by using it in petrochemicals, they say. With about 300,000 vehicles, the Italians have a network of 280 filling stations to support their use of the gas. Other large users are Argentina with about 400,000 vehicles and converting 3,000 more every month. In India the CNG usage started in 1992 and so far about 25,000 vehicles are running on CNG in Mumbai, Delhi, Vadodra, Surat and Ankleshwar. The major difference between a petrol vehicle and a CNG one is the fuel system.
Natural gas is compressed and stored onboard the vehicle in cylinders installed in the rear.
Natural gas passes from the cylinders through a valve and travels through a high-pressure fuel regulator located in the engine compartment. A flip of a switch can change the fuel. A dual-fuel vehicle runs on diesel fuel only or on diesel and natural gas simultaneously. The combustion of the diesel fuel serves to ignite the natural gas. As oppossed to these, a dedicated CNG vehicle runs on natural gas only.