A method of skip-firing an engine system, said engine system having a plurality of combustion chambers and a fuel-injection system and said engine system being operable in a normal injection mode without skip-firing and in a skip-fire injection mode, said method comprising: detecting whether said engine system is experiencing a predetermined low load condition for applying the skip-fire injection mode, when said predetermined low load condition is detected, determining and selecting at least one combustion chamber of said plurality of combustion chambers designated for skip-firing during a next cycle, skip-firing said selected at least one combustion chamber for a given duration, determining whether said engine system continues experiencing the low load condition during said given duration, and, if so, repeating determining and selecting at least one combustion chamber of said plurality of combustion chambers to skip-fire during said next cycle, and if not, returning said plurality of combustion chambers to the normal injection mode without skip-firing, characterized in that the system is operated with a main fuel and a pilot fuel, the main fuel and the pilot fuel being two different fuels, when firing a specific combustion chamber an amount of pilot fuel sufficient to ensure stable combustion in said combustion chamber is injected into said combustion chamber and an amount of main fuel appropriate to satisfy the demanded engine load is injected into said combustion chamber, and if the engine system is operated at the predetermined low load condition it is using a lower ratio of pilot fuel to a total fuel quantity measured on an energy basis in a skip-fire injection mode compared to the engine system operated in the normal injection mode without skip-firing. detecting whether said engine system is experiencing a predetermined low load condition for applying the skip-fire injection mode, when said predetermined low load condition is detected, determining and selecting at least one combustion chamber of said plurality of combustion chambers designated for skip-firing during a next cycle, skip-firing said selected at least one combustion chamber for a given duration, determining whether said engine system continues experiencing the low load condition during said given duration, and, if so, repeating determining and selecting at least one combustion chamber of said plurality of combustion chambers to skip-fire during said next cycle, and if not, returning said plurality of combustion chambers to the normal injection mode without skip-firing, characterized in that the system is operated with a main fuel and a pilot fuel, the main fuel and the pilot fuel being two different fuels, when firing a specific combustion chamber an amount of pilot fuel sufficient to ensure stable combustion in said combustion chamber is injected into said combustion chamber and an amount of main fuel appropriate to satisfy the demanded engine load is injected into said combustion chamber, and if the engine system is operated at the predetermined low load condition it is using a lower ratio of pilot fuel to a total fuel quantity measured on an energy basis in a skip-fire injection mode compared to the engine system operated in the normal injection mode without skip-firing.