A method for upgrading a petroleum oil by a hydroprocessing reaction in which the oil is hydrogenated, includes the steps of: a. forming a liquid reaction mixture of the oil with water and an amphiphilic liquid in predetermined proportions to thereby render the oil and water miscible; b. introducing the liquid reaction mixture into an electrolytic reactor having one or more cathodic elements formed from a porous high surface area,conductive material; c. operating the reactor to form reactive hydrogen atoms whereby the oil is hydrogenated by the hydrogen atoms; d. removing the liquid mixture from the reactor; and e. separating the hydrogenated upgraded oil from the amphiphilic liquid and any remaining water, e.g., by distillation, recovering and recycling the amphiphilic liquid for use.