What do we call a fuel's ability to resist knocking during combustion?

The term that refers to a fuel's ability to resist knocking during combustion is known as the octane rating. The octane rating is a measure of a fuel's stability under compression; higher octane ratings indicate that a fuel can withstand greater compression before igniting spontaneously. Knocking, or pre-ignition, occurs when the air-fuel mixture ignites prematurely in the engine's cylinder, which can lead to engine knocking and potentially cause damage. Fuels with a higher octane rating are often used in high-performance engines and engines designed for high compression ratios, where knocking can be more prevalent.

The concepts of efficiency rating, combustion stability, and fuel resistance do not specifically relate to the phenomenon of knocking in the way that octane rating does. While they may pertain to various aspects of fuel performance or combustion processes, they do not capture the specific characteristic of how well a fuel resists knocking. Therefore, the octane rating is the most accurate and relevant term for this specific property of fuel.