A system for reducing polluting emissions of diesel engines includes a hydrogen gas generator that mixes the hydrogen gas with diesel fuel during certain operations phases of the engine. A default program mixes no hydrogen gas with the diesel fuel. A first operational program, during a cold start, mixes the hydrogen gas and diesel fuel in a 1:1 ratio. A second operational program, during a stabilization phase, mixes the hydrogen gas and diesel fuel in a 1:3 ratio. A third operational program, during a hot start phase, mixes the hydrogen gas and diesel fuel in a 1:2 ratio.