The octane number is determined by comparing the characteristics of a gasoline to isooctane (2,2,4-trimethylpentane) and heptane. ... Cracking, isomerization, and other refining processes can be used to increase the octane rating of gasoline to about 90. Anti-knock agents may be added to further increase the octane rating.

Is isooctane the same as octane?

The reference substance for the octane number is not octane.

It is actually a branched isomer of octane with the traditional name “isooctane”.

What is isooctane used for?

It is an important component of gasoline, frequently used in relatively large proportions to increase the knock resistance of the fuel. Strictly speaking, if the standard meaning of 'iso' is followed, the name isooctane should be reserved for the isomer 2-methylheptane.