Have you ever wondered what the octane rating in your gasoline is for?

To understand the concept of the octane rating, one must go back to the premise that most cars nowadays run using a four-stroke gasoline engine. One of the fuel combustion in engines is compression – and there is a certain degree of compression that can be achieved with for gasoline before it spontaneously ignites. What must ignite the gasoline is the spark from the spark plug. If the gasoline spontaneously burns once it is compressed (and not yet ignited by the spark plug) – knocking of the engine occurs, and this consequence damages the car engine.

The octane rating of a gasoline dictates the degree of compression of the fuel product before it spontaneously ignites. The term octane rating is derived from the fact that the eight-carbon compound octane tolerates compression well, compared to heptane, the seven-carbon fuel which spontaneously ignites upon compression. The regular 87 octane rating gasoline handles only minimal compression and is either a 87% octane and 13% heptane blend or another mixture of hydrocarbons which achieve the same octane performance rating of 87 as with the 87%/13% octane-heptane blend.

And in some cars, to improve the horsepower, they improve the compression ratio of the engine (the amount of compression before the spark ignition) and these engines require higher octane rating fuels – hence the term “high performance engine”.

During the First World War, the addition of the compound tetraethyl lead to gasoline greatly improved its octane rating. However the lead clogs the catalytic converter of an engine, destroys it in minutes and as a result a noxious amount of lead is released from the engine along with other toxic substances that should have been neutralized by the catalytic converter. Because lead in the environment is a health threat, they banned the use of tetraethyl lead, raising gasoline prices.

Now there is unleaded gasoline with good octane ratings, as well as gasoline blended with high octane rating compounds derived from chemical processing.