A method for adapting an engine to an octane number of fuel by incrementing an initial octane number. Starting with a reference setting of a spark advance in an engine operating range for a given octane number, the engine operating range being divided into a plurality of zones, each including an anti-pinging corrective value of the spark advance of the reference setting, the engine is switched to a reference setting that corresponds to a higher octane number: when a top dead center counter, incremented if the advance correction in the current zone is lower than a predetermined threshold, exceeds a predetermined threshold, or when a counter of the number of the zones in which the advance correction loop is lower than another threshold value, exceeds a multi-zone threshold.