To develop a new fuel of low cost and low pollution which can be used as a substitute fuel for diesel oil normally used for the diesel internal combustion engine, by utilizing the good point of an alcohol component.

This fuel comprises special heavy oil, first class heavy oil or regenerated heavy oil regenerated by an apparatus for reduction to oil etc., as the base fuel, and is mixed with alcoholic ingredients including normalpropyl alcohol, isobutyl alcohol, secondarybutyl alcohol or the like each in sizable percentage to maintain the cetane number at the same level as the generally used diesel oil, to draw out the good point possessed by the alcohol of reducing effect of the exhaust gas, while mismatching of engine conditions and possibilities of engine damaging due to deterioration of gland packing and rubber materials in the fuel system which are considered as shortcomings of the alcoholic ingredients are reduced as much as possible by regulating the mixing ratio of individual ingredients. Further, a synergistic effect by using regenerated heavy oil could be seen in the solving efforts which may be favorable to environmental problems as well.