CNG is an compressed natural gas that is widely used in India ,in bus,truck,car, and Auto,moterbyake etc. At low pressure, it is too bulky to be stored or be of much value to car and bus/truck/car engines. Compressed at high pressure, the energy stored in the vehicle increases giving the vehicle a reasonable range between refills

CNG is made mainly of methane whereas LPG is a mixture of propane, butane and some other minor chemicals. Methane remains a gas even when compressed to very high pressures, hence the name Compressed Natural Gas (CNG). Natural gas can be liquified to give Liquefied Natural Gas (LNG) at the very low temperature of-160 centigrade. LNG has been used experimentally as vehicle fuel in USA and Germany. Propane and butane are gases at normal room temperature and pressure but become liquid under moderate compression; hence the name liquefied Petroleum Gas (LPG). CNG is a 100% locally produced fuel whereas LPG becomes available from two different sources i.e. refineries and oil wells. The LPG available from the refineries is a product mostly of imported crude oil and the available from wells is the form of associated gases. In addition, some LPG is also imported. Both LPG and CNG can be used as transport fuel but the Government wants to use LPG in the domestic sector, since it can easily be transported to such areas where natural gas pipelines are not in place to replace Kerosene and to prevent deforestation. As a result of research, development and efforts of the GGL and others company

In the past, gas-fuelled automobiles used LPG. Today it is compressed natural gas (CNG) that is in use. Methane is the prime component of CNG while LPG is a blend of propane, butane and some other chemicals.

An LPG-fuelled vehicle will not run on CNG as the two fuels are different from each other, have differing calcrific values and need different air-fuel ratios for combustion. CNG has to be stored at relatively higher pressure in a cylinder than LPG, so the same cylinder cannot be used for both gases. A vehicle will need specific conversion for CNG operation.

CNG is filled in the cylinder up to a maximum of 200kg/cm(about 3000psi/g). CNG has a 700 degree Centigrade ignition temperature compared to 455 degree Centigrade for petrol. The range of 4 to 14 per cent in which CNG mixes with air by volume for combustion is small. Storage is far safer than for petrol, as CNG cylinders are designed and built from special materials and to high safety specifications.

Use of CNG serves to extend life of lubricating oil as CNG will not contaminate or dilute crankcase oil. Fouling of plugs is eliminated and plug life is enhanced as CNG does not contain any lead. CNG enters the engine as gas while petrol comes in as spray or mist which washes down the lubricating oil from the piston ring area to raise the rate of engine depreciation. This reduces maintenance costs and engine life goes up.

A major positive aspect of CNG use is that being a natural gas (methane content) its exhaust emissions contain just water vapour and minuscule quantity of carbon monoxide, no carbon or other particles. Being virtually pollution free CNG driven vehicles meet the most stringent of emission standards worldwide.

The petrol carburettor is retained during conversion for CNG so that the vehicle will still run on petrol. A switch on the dashboard allows one to make instant changes of fuel sources.

Savings on fuel cost by using CNG will depend on size and fuel consumption characteristics of the vehicle, as well as mileage. As we have seen in the CNG Omni the cost per kilometre incurred was nearly half that of the costs incurred by the petrol van.

Occasional use of petrol serves to lubricate the carburettor besides making for better running of the engine.

Four key features make CNG a safer fuel than petrol, diesel or LPG. With specific gravity of 0.587, it is lighter than air so in case of leaks, it rises up and dissipates into air. (Other fuels form puddles on the ground in case of leaks.) CNG has a 700 degree Centigrade ignition temperature compared to 455 degree Centigrade for petrol. The range of 4 to 14 per cent in which CNG mixes with air by volume for combustion is small. Storage is far safer than for petrol, as CNG cylinders are designed and built from special materials and to high safety specifications.

Easy starts, steady idling and smooth acceleration are virtues of CNG run vehicles. Power loss of 5-15 per cent means that acceleration is slower, which can be eradicated with spot-on tuning of the CNG kit, by advancing spark timing to derive benefit of its high octane rating. However the power loss is less than noticeable in city driving.

The CNG kit is easy to service and durable to boot. For optimum efficiency regular checks, every 10,000km .