PURPOSE: To reduce a volume of fuel by the use of water and miscellaneous oil and to enable cleaning of exhaust gas, by a method wherein, at the knotting part of the exhaust pipe of an engine, a water pipe and a miscellaneous oil pipe are attached to the exhaust pipe so that they can be inserted therein and taken out therefrom.

CONSTITUTION: An exhaust multi-branch pipe 1 and a suction multi-pipe 2 of a multicylinder internal-combustion engine are mounted in adjacent to each other on the same side of an engine body. A water pipe 3 for water gas and a miscellaneous oil pipe 8 for miscellaneous oil gas are installed to the interior of the multi-branch pipe 1. A driving force for a turbine is generated by the use of water gas, which is activated by chemical reaction occurring by means of heat and kinetic energy of exhaust gas from the internal-combustion engine. This reduces a volume of fuel and enables cleaning of exhaust gas.