An octane number as determined by the motor method of the American Society for Testing and Materials, used chiefly for high engine speeds and loads; abbreviated MON.
Origin
1950s; earliest use found in ASTM Manual Engine Test Methods for rating Fuels.
Definition of motor octane number in US English:
motor octane number
noun
An octane number as determined by the motor method of the American Society for Testing and Materials, used chiefly for high engine speeds and loads; abbreviated MON.
Origin
1950s; earliest use found in ASTM Manual Engine Test Methods for rating Fuels.