Octane Number
What is Octane Number?
The octane number (octane rating) is a measure of a fuel's resistance to knocking (premature detonation) in a spark-ignition internal combustion engine, with higher values indicating greater resistance. It is defined relative to reference fuels: iso-octane (2,2,4-trimethylpentane) has an octane rating of 100 and n-heptane has a rating of 0. Branched and aromatic hydrocarbons have high octane numbers, while straight-chain alkanes have low values; antiknock additives such as tetraethyllead and ethanol improve octane ratings.
Key Facts
Frequently Asked Questions
The octane number (octane rating) is a measure of a fuel's resistance to knocking (premature detonation) in a spark-ignition internal combustion engine, with higher values indicating greater resistance. It is defined relative to reference fuels: iso-octane (2,2,4-trimethylpentane) has an octane rating of 100 and n-heptane has a rating of 0. Branched and aromatic hydrocarbons have high octane numbers, while straight-chain alkanes have low values; antiknock additives such as tetraethyllead and ethanol improve octane ratings.