The Octane Number of a fuel simple describes the fuel's resistance to Detonation. It
does not relate to the amount of Octane present. The "Octane" referred to is iso-octane, with the full name
2,2,4-Trimethylpentane. All other fuels are rated
against this to give an Octane Number. Currently the "Research Octane Number" or RON is used in the UK,
and the US use a system called the Anti-Knock Index, AKI which is an average between RON and MON.
MON is the "Motor Octane Number" which provides a simulation closer to a modern engine, and gives values usually between 5 and 10 points lower.
The use of differing formats is not a big problem, as the numbers are best thought of as relative values, but caution needs to be exercised
when talking of Octane numbers and fuel ratings between contents, as a US 95 fuel may have the same knock resistance as a
97/98 rated fuel in Europe.
By definition, iso-octane would have an Octane number of 100.
Fuels are tested in a special test engine, and forced to detonate. This is compared with a fuel made of iso-octane (100 RON)
and n-heptane (0 RON). If the test fuel reacts similar to a mix of 95% iso-octane, and 5% n-heptane, it will be
rated at 95 RON. There are a number of additives in modern fuels to increase the detonation resistance, and increase the Octane Number.
With higher Octane rating, the point of Ignition can be advanced, with the aim of getting more usable
power out of the burn. Higher Octane fuels will allow the increased Ignition advance, and provide the opportunity for the
engine to create more power. Higher octane fuels don't increase the power themselves, they just allow the ignition to be advanced
to a more powerful angle without the dangerous detonation.
The timing of the spark is all important to the production of power. Too early or too late can waste the energy, and if earlier still,
the mix will create a pressure wave from burning gasses, explode and can melt your engine!
Petrol has long been the favoured fuel source for light vehicles. Some of the first uses of petrol
was for delousing and a cleaning fluid until the rise of the Internal Combustion Engine when it became as popular as it is now.
It is created from a fractionating process from Crude Oil, and various products are made, Tar and Paraffin will be
drained off from the bottom of the fractionating column, Diesel and other lighter molecules are removed further up,
and at the top, Petrol is
drawn off, and the remaining gasses are what we know as LPG, Liquefied Petroleum Gas.