Abstract: A process encompassing hydrogen and oxygen gases as a partial fuel source when utilized together with a fossil-based fuel to power conventional internal combustion engines. Hydrogen and oxygen gases are produced by electrolysis in an electrolyser unit(s), on-demand and on-board a vehicle, or in stationary applications, eliminating the need of highly-pressurized hydrogen storage tanks When said gases are introduced into the combustion chamber of the engine, via the air intake assembly, they increase the efficiency of the combustion burn by enriching the air to fuel ratio, resulting in a reduction of the fossil-based fuels required for optimum engine performance, said gases effectively becoming a partial hybrid fuel source. The process includes scalability for all size and types of installations, cold-weather applications and longer operating capabilities. As an additional benefit, in direct correlation, this process reduces carbon dioxide emissions, and, in varying quantities, other greenhouse gas emissions.