ISO 5164:2014 establishes the rating of liquid spark-ignition engine fuel in terms of an arbitrary scale of octane numbers using a standard single-cylinder, four-stroke cycle, variable compression ratio, carburetted, CFR engine operated at constant speed. Research octane number (RON) provides a measure of the knock characteristics of motor fuels in automotive engines under mild conditions of operation.
ISO 5164:2014 is applicable for the entire scale range from 0 RON to 120 RON, but the working range is 40 RON to 120 RON. Typical motor fuel testing is in the range of 88 RON to 101 RON.
ISO 5164:2014 is applicable for oxygenate-containing fuels containing up to 4,0 % (m/m) oxygen and for gasoline containing up to 25 % (V/V) ethanol.