number is defined as the percentage by volume of iso-octane
(2, 2, 4-trimethylpentane) in a mixture on n-heptane and
iso-octane. Octane number is a measure resistance of
gasoline (petrol) to knocking in spark ignition internal
a gasoline contains 80% of iso-octane and 20% of n-heptane
then the octane rating of the fuel is 80.
having high compression ratio require high octane rating
fuel to resist the knocking.