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Different fuel types

Automotive columnist: , Updated:

Fuels that derive from petroleum, such as gasoline and diesel, are called hydrocarbons and are composed of hydrogen and carbon. Petroleum oil’s composition depends largely on its place of origin. Its sulphur and other mineral content can vary from one oil field to the next. This crude oil has to undergo a series of transformations before becoming the final fuel products that we so greatly depend on today.

Refining Stages

Diesel fuel

As an end product, diesel fuel is the result of a simpler processing of the crude oil than that required for gasoline. Elimination of the impurities and distillation are indispensable in both cases. Then, sulphur content is reduced thanks to hydrodesulfurization(HDS), followed by hydrotreating. Since 2006 (for environmental reasons) only diesel with very low sulphur content is sold in North America and Europe.

Diesel fuel quality is measured according to its cetane number. The lowest legally allowable cetane number is 51. The more this figure increases, the better the diesel fuel quality, so cleaning agents are often added to it. Good quality diesel fuel will have properties which favour ignition and combustion.

Given that the diesel engine has no spark plugs, the air-diesel fuel mixture has to ignite and combust, because of simple compression alone.

This low heat resistance is the contrary to what qualifies gasoline. To produce gasoline, refining must be continued. It’s during catalytic reforming that the octane rating of the gasoline is determined.

The octane rating measures the thermal resistance of a fuel. The higher the rating, the less easily the substance will ignite.

At the pump, you’ll find gasoline types with various octane ratings, which could range from 87 to 94. ‘Regular’ gas has the lowest octane rate, i.e. ‘87’, and has poorer heat resistance.

Different fuel types

‘Super’ gasoline is recommended for engines equipped with turbo or superchargers, or those with high compression ratios. These types of engines produce increased heat.

In a gas engine, combustion of the mixture compressed in the piston chamber has to take place when ignited by the spark plug, not before. If the gas type used is of poorer quality, heat created by the compression will sometimes be enough to produce combustion, resulting in a detonation. This premature explosion must be avoided because it can cause considerable damage to engine components.

You should ensure that the quality of the particular gas type you choose keeps pace with the advanced technologies that are showcased by the vehicle you drive.

Alternate energy sources

Clean fuels like diesel (very low in sulphur), as well as technologies developed to decrease gas consumption and greenhouse gas emissions, puts us all on the right road when it comes to protecting our planet.

Besides hybrid and electric cars (with a big bet on lithium-ion technology), there are other potential energy sources that could free us from our dependence on oil.

Cars running on hydrogen, ethanol, biodiesel or natural gas open up many avenues to be explored.