Motor Octane Number (MON) evaluates gasoline stability using a test engine running at higher speeds, higher temperatures, and variable ignition timing compared to standard tests. It represents how the fuel behaves under heavy load, such as towing or wide-open throttle acceleration. At the pump, the final octane rating displayed is usually the average of this number and the Research Octane Number.
The race gas has a MON of 110, which keeps it from detonating when we crank up the boost.
Pump gas ratings in North America use the (R+M)/2 method, meaning the displayed octane is the average of the RON and MON values.
Do not mix it up with
- RON: RON measures fuel behavior under mild idle conditions, while MON tests it under severe, high-load conditions.
Related terms
RON
Research Octane Number, a standard rating of a fuel's resistance to engine knocking.
Anti-knock index
The standard numerical rating of a fuel's resistance to premature ignition.
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.