Abstract: A high-power liquid fuel composition for spark-ignition engines is provided. The fuel composition has a RON greater than or equal to 95 and a MON greater than or equal to 85, the RON and MON values being measured according to the ASTM D 2699-86 standard or D 2700-86 standard, and includes at least one C4-C5 unsaturated alcohol. The disclosure also relates to the use of a C4-C5 unsaturated alcohol, preferably 3-methyl-2-butene-1-ol or 3-methyl-3-butene-1-ol, in a petrol fuel composition, for improving the power of a naturally-aspirated or turbocharged spark-ignition engine, during the combustion. The disclosure also relates to a process for preparing such a fuel composition.