A measure of gasoline quality calculated as the average of the Research Octane Number and the Motor Octane Number. It dictates how much cylinder compression and ignition advance an engine can run before the fuel-air mixture detonates spontaneously.
Heard on the job
This high-compression build requires an anti-knock index of at least 91 to keep the pistons intact.
Also heard as
- AKI
- pump octane number
- PON
Do not mix it up with
- RON: RON is only one half of the equation, while AKI averages RON and MON for the final pump rating.
Related terms
Knock
An abnormal and damaging combustion event where the air-fuel mixture self-ignites prematurely.
Detonation
An uncontrolled secondary explosion in the combustion chamber that causes severe engine damage.
RON
Research Octane Number, a standard rating of a fuel's resistance to engine knocking.
MON
A measure of a fuel's resistance to detonation under severe operating conditions.