A method of operating an internal combustion engine having a plurality of cylinders (1, 2, 3) and pistons (4, 5, 6) respectively supported therein. During an expansion stroke of the piston (4, 5, 6) of at least one of the cylinders (1, 2, 3), combusted gas from said at least one cylinder is delivered to at least one other cylinder. Delivery is effected by the pressure differential between the gases in the at least one cylinder supplying the gas and the at least one other cylinder receiving the gas. Further, the gas is delivered from the at least one cylinder to the at least one other cylinder independently of the exhaust system of the engine.