octane number

American  

noun

1. (of gasoline) a designation of antiknock quality, numerically equal to the percentage of isooctane by volume in a mixture of isooctane and normal heptane that matches the given gasoline in antiknock characteristics.

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octane number British  

noun

1. a measure of the quality of a petrol expressed as the percentage of isooctane in a mixture of isooctane and n -heptane that gives a fuel with the same antiknock qualities as the given petrol

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octane number Scientific  

1. A numerical representation of the ability of a fuel to resist knocking when ignited in the cylinder of an internal-combustion engine. The octane number of a given fuel is determined by comparing the amount of knocking that fuel causes when combusted with the amount of knocking caused by two standard reference fuels, isooctane (which resists knocking and has an octane number of 100) and heptane (which causes knocking and has an octane number of 0). The octane number is then assigned as the percentage of isooctane required in a blend with normal heptane to match the knocking behavior of the fuel being tested.

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Etymology

Origin of octane number

First recorded in 1930–35

Example Sentences

Now that you know what the octane number means, it’s important to understand what makes each fuel type useful and unique.

From Seattle Times • Aug. 16, 2021

Mid-grade gasoline will typically have an octane number between 88 and 90, and it offers better performance than standard gas.

From Seattle Times • Aug. 16, 2021