iso-octane(redirected from 2,2,4-Trimethylpentane)
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A paraffin hydrocarbon fuel, defined as 2,2,4-trimethylpentane, which is used as a standard in the rating of fuels. This knock quality of fuel is expressed as a percentage by volume of iso-octane in a mixture with normal heptane that has the same knocking characteristics as the fuel under question. Fuel with an 87 octane rating is equivalent to a mixture of 87% iso-octane and 13% heptane.