This study present the performance optimization of a spark ignition (SI) engine using gasoline fuels with variations of research octane number (88, 92, and 98) with 40 volume % of bioethanol. The optimization is done by setting the spark ignition time (2 o CA advanced) and fuel injection duration (10% reduction) of the engine control module. The engine was tested using an engine dynamometer test to obtain the performance data at the shaft speed of 1000, 1500, 2000, and 2500 RPM and wide-open throttle conditions. From the results of this study, we conclude that optimizing the engine control strategy can lead to the improvement of engine power, torque, and specific fuel consumption which are more significant with the usage of fuels with higher octane number.