To provide a method and an apparatus therefor for producing a modified fuel oil, capable of reducing fuel consumption at practical levels through modifying a fuel oil.

The apparatus comprises a container 6 electrically insulated to the ground and in which a fuel oil 5 to be modified is to be contained and an electron generator 7 for periodically charging electrons into the fuel oil 5 in the container 6. By periodically charging the fuel oil 5 in the container 6 with electrons, unsaturated carbon atoms in the fuel oil 5 are decreased and saturated carbon atoms constituted of single bonds alone are increased. As a result of increasing such saturated carbon atoms, the number of hydrogen atoms in the fuel oil is increased. Thus, the explosive power of the fuel oil is increased, resulting in reducing the fuel oil consumption.