An engine control system includes: a delay estimating unit configured to estimate a auto-ignition delay based on first parameters including a composition of fuel gas; a auto-ignition predicting unit configured to predict a auto-ignition timing based on the auto-ignition delay; a completion predicting unit configured to predict a combustion completion timing of the fuel gas; and an operation control unit configured to control an engine based on a result of comparison between the auto-ignition timing and the combustion completion timing.