Definition of octane number in English:

octane number

Line breaks: oc¦tane num¦ber
(also octane rating)


  • A figure indicating the anti-knock properties of a fuel, based on a comparison with a mixture of isooctane and heptane.
    More example sentences
    • In particular, the formation of branched alkanes increases the octane number and combustibility of the resulting hydrocarbon.
    • Using a fuel of a higher octane rating than that recommended for your car doesn't improve its performance.
    • The higher the octane number you see on a gas pump, the more the fuel can be compressed before it explodes.

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