Fuel Characteristic | Petrol | Diesel | CNG | LPG |
Urban Air Pollution | Moderate to low emissions of hydrocarbons (HC) and oxides of Nitrogen (NOx). Low particle (PM) emissions | High NOx, low HC emissions. High PM emissions relative to other fuels even with reduced sulphur levels. By far the highest adverse impact on public health. | HC (methane) emissions can be high. Moderate to low NOx. Very low PM. | Low Nox and moderate to low HC emissions. Very low PM. |
Global Warming (Greenhouse) | Moderate CO2, low methane (CH4) emissions. | Lower CO2, low CH4 and HC. Airborne PM may increase global warming. High NOx levels may result in elevated N20 emissions. | Potentially lowest CO2 of all fuels, but this can be offset by the very high greenhouse impact of methane (CH4) emissions from these engines. | Tailpipe CO2 emissions lie between petrol and diesel. Lifecycle CO2 comparable to diesel, lower than petrol and CNG. Negligible CH4 emissions. |
Engine Noise | Low | High | Low | Low |
Application | Lowest cost fuel system, so attractive for cars and light commercials. | Complex high pressure fuel system increases cost, but most fuel efficient. Very durable and reliable in heavy duty applications. | High cost and limited range. Preclude use in light duty vehicles and in areas where there is no pipeline gas. | Cost, range and on road performance equivalent to petrol in light duty vehicles. Engines now available for buses and medium trucks. Not constrained to depot-based operations. |
Retail Availability | Nationally Available | Nationally Available | Limited | Nationally Available |