A robust, non-aqueous, and oil-soluble organic peroxide oxidant is employed for oxidative desulfurization and denitrogenation of hydrocarbon feedstocks including petroleum fuels. Even at low concentrations, the non-aqueous organic peroxide oxidant is extremely active and fast in oxidizing the sulfur and nitrogen compounds in the hydrocarbon feedstocks without catalyst. Consequently, the oxidation reactions that employ the non-aqueous organic peroxide oxidant take place at substantially lower temperatures and shorter residence times than reactions in other oxidative desulfurization and denitrogenation processes. As a result, a higher percentage of the valuable non-sulfur and non-nitrogen containing components in the hydrocarbon feedstock are more likely preserved with the inventive process. Desulfurization and denitrogenation occur in a single phase non-aqueous environment so that no phase transfer of the oxidant is required.