LPG is the most common alternative fuel for SI engines but play a minor role in the total energy consumption is accounted for road transport because the fuel supply is greater than demand the price level remains low It causes high octane fuel LPG engines with higher compression ratio than gasoline engines and therefore have higher thermal efficiency, However, LPG-fueled vehicles have become style It has a thermal efficiency rating and they are less than optimal Well to wheel energy consumption of LPG is less than petrol and more than diesel. In Light vehicles NOX emissions the wheel wells close to the figures of petrol but it is less related emissions low emission of fine particles is more pronounced in heavy trucks. Since LPG is a gas at ambient temperature and pressure it into liquid at a pressure of about 6 to 8 times and then stored in pressurized tanks LPG storage tank almost doubled in volume and 1.5 times the weight of an amount of energy equal to its petrol tank this fuel as fuel is not considered generally safe because it is heavier than air and in case of leaks, vapor in the earth, and increases the risk of explosion.
