Octane and its rating

The octane number is a measure of a gasoline’s antiknock performance, which is its ability to resist knocking as it burns in the combustion chamber. There are two test methods to measure the octane number of a gasoline: the research octane number (RON) and the motor octane number (MON). The RON of a given gasoline is always greater than its MON, and the difference between the two numbers indicates the sensitivity of a gasoline to changing operating conditions. Gasoline specifications typically provide minimum RON and/or MON requirements.

In some countries such as the United States (U.S.) and Mexico, gasoline is labeled with its antiknock index (AKI), also called the octane index. The AKI is calculated with the formula: (RON+MON)/2. It is an approximation of the road oc