NOVELTY - The device has a battery (6) that supplies electrical power to a pure water replenishable electrolytic bath (1) to allow the bath to electrolyze pure water into hydrogen and oxygen that are fed into a fuel conduit through a first gas supply tube (14). A second supply tube (52) supplies the hydrogen and oxygen to a hydrogen-oxygen fuel cell (5) for chemical reaction that generates electrical power to charge the battery, and for the chemical reaction of the cell generating a product of pure water that is supplied through a pure water tube (53) to replenish the bath.    USE - Ancillary device for enhancing fuel combustion efficiency of an engine e.g. diesel and petrol engine of vehicles. Uses include but are not limited to electrical vehicles, hybrid vehicles, solar power vehicles and an automobile.    ADVANTAGE - The device ensures supplying hydrogen and oxygen to the hydrogen-oxygen fuel cell through the second gas supply tube for chemical reaction that generates electrical power to charge the battery, where the chemical reaction of the hydrogen-oxygen fuel cell generates a product of pure water that is supplied through the pure water tube to the electrolytic bath for realizing circulative and cyclic utilization for electrolysis. The device generates auxiliary fuel to be supplied to a fuel supply system of an automobile for being fed to an engine cylinder so as to reduce fuel consumption rate, improve fuel combustion efficiency, and generate electrical power in an operation cycle to charge an automobile battery and recover the produced pure water for circulative and cyclic use. The device ensures that a filter system is arranged in the exhaust pipe of an automobile engine so as to filter the exhaust gas discharged from the automobile engine for preventing environment from polluting caused by emission of exhaust that contains high contents of pollutant components and generating smokes. The device is operated under the control of an automobile computer, and automatically activates or deactivates the electrolytic bath at the time when the automobile power supply is activated or cut off, and can stably control voltage and current during operation of electrolysis of pure water so as to control the speed of generation of hydrogen and oxygen that are fed continuously into the fuel pipe under negative pressure. The device can automatically close a throttle valve to cut off supplies of hydrogen and oxygen when electrical power is cut off, and allows a check valve to prevent the fuel to flow into the electrolytic bath through the gas supply tube when power is set on.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an automobile fuel supply system.    Pure water replenishable electrolytic bath (1)    Hydrogen-oxygen fuel cell (5)    Battery (6)    Gas supply tubes (14, 52)    Pure water tube (53)