$CNG ($Compressed Natural Gas$)$ is now used as a fuel for transport vehicles because it is less polluting. Compressed Natural Gas $(CNG)$ (methane stored at high pressure) can be used in place of gasoline (petrol), Diesel fuel and propane $(LPG).$ $CNG$ combustion produces fewer undesirable gases than the fuels mentioned above.
In India, the Petroleum Conservation Research Association $(PCRA)$ advises people on how to save petrol/ diesel while driving. Their tips are: Drive at a constant and moderate speed as far as possible, switch off the engine at traffic lights or at a place where you have to wait, ensure correct tyre pressure, and regular maintenance of the vehicle. But keeping the engines on always would increases the consumption.
| $p$ | $q$ | $u$ | $v$ | $w$ | $x$ |
| Petroleum | Coal | Petroleum gas | Bitumen | Coal gas | Coke |
| $p$ | $q$ | $u$ | $v$ | $w$ | $x$ |
| Coal | Petroleum | Coal gas | Coke | Petroleum gas | Bitumen |
| $p$ | $q$ | $u$ | $v$ | $w$ | $x$ |
| Coal | Petroleum gas | Coal | Charcoal | Gasoline | Coal tar |
| $p$ | $q$ | $u$ | $v$ | $w$ | $x$ |
| Petroleum | Coal | Gasoline | Bitumen | Natural gas | Coke |
| $p$ | $q$ | $u$ | $v$ | $w$ | $x$ |
| Coal | Petroleum | Coal gas | Coke | Petroleum gas | Bitumen |
|
$p$
|
$q$
|
$u$
|
$v$
|
$w$
|
$x$
|
|
Coal
|
Petroleum
|
Coal gas
|
Coke
|
Petroleum gas
|
Bitumen
|
$CNG$ consists primarily of methane but also contains ethane, propane and heavier hydrocarbons. It also contains small amounts of nitrogen, carbon dioxide, hydrogen sulphide and very little amount of water.
The most common sources of energy used in automobiles are petroleum and diesel.
