[mrtexas]

"Actually octane is a hydrocarbon that is blended into fuel to prevent it from auto igniting. It's use maintains an orderly flame front across the combustion chamber. The octane rating is used to rate the performance of the particular fuel being used."

An iso-octane mixture is made in many refineries in a unit called an Alkylation unit. BTW an octane rating is a measure of the resistance of gasoline to ignition. The higher the octane rating the more resistant to ignition. The unknown sample is compared to a mixture of iso-octane with a rating of 100 and n-heptane with a rating of 0.