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.
‘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.