High Quality Content by WIKIPEDIA articles! Octane is a hydrocarbon and an alkane with the chemical formula CH3(CH2)6CH3. Octane has many structural isomers which differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (isooctane) is used as one of the standard values in the octane rating scale. As with all low-molecular weight hydrocarbons, octane and its isomers are very flammable. It is a component of gasoline (petrol).