Definition - What does Octane Level mean?
Octane Level, also known as octane rating or octane number is the standard measure of the performance fuel for an internal combustion engine. A Fuel with a high Octane level can withstand more compression before igniting and can be used in the high performance engines of gasoline which require high ratios of compression. Fuels with low ratings are considered ideal for the diesel engines whereby instead of compressing the fuel they compress air and inject the fuel into the air that is heated up due to the compression.
Petropedia explains Octane Level
The ratings of gasoline are measured in a test engine defined by the comparison with the blend of heptane and trimethylpentane which have a similar anti-knocking ability as the fuel under test. The rating does not indicate the content of the energy in the fuels. It is considered as the tendency of fuel to burn in a limited manner instead of exploding uncontrollably. Octane level is considered as the measure of the ability of fuels to resist the knocking. When the octane level is raised by mixing ethanol, the energy content reduces per volume.