follow Dictionary.com

Stories We Like: Novels For Language Lovers

octane number

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.
Also called octane rating.
Origin
1930-1935
1930-35
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source
British Dictionary definitions for octane-rating

octane number

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
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Cite This Source
octane-rating in Science
octane number  
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
Encyclopedia Article for octane-rating

octane number

measure of the ability of a fuel to resist knocking when ignited in a mixture with air in the cylinder of an internal-combustion engine. The octane number is determined by comparing, under standard conditions, the knock intensity of the fuel with that of blends of two reference fuels: iso-octane, which resists knocking, and heptane, which knocks readily. The octane number is the percentage by volume of iso-octane in the iso-octane-heptane mixture that matches the fuel being tested in a standard test engine. See also knocking

Learn more about octane number with a free trial on Britannica.com
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source

Word of the Day

Difficulty index for octane number

Few English speakers likely know this word

Word Value for octane

8
10
Scrabble Words With Friends

Quotes with octane-rating

Nearby words for octane-rating