Abstract: An energy fortified diesel fuel is provided containing a hydrocarbon additive wherein greater than 50% vaporizes at or above about 650.degree. F. and diesel fuel of which about 90% of the diesel fuel vaporizes at or below about 640.degree. F. or about 95% of the diesel fuel vaporizes at or below about 698.degree. F. This energy fortified diesel fuel is made by distilling a heavy hydrocarbon fraction such as slurry oil or heavy cycle oil obtained from an FCC unit or a heavy hydrocarbon fraction obtained from a steam cracker unit at a temperature of between about 500 and 750.degree. F. and at a pressure of between about 1 mm Hg and 10 psig to remove contaminants, removing distillate from this distillation, and mixing the distillate with diesel fuel, wherein about 90% of the diesel fuel vaporizes at or below about 640.degree. F. or about 95% of the diesel fuel vaporizes at or below about 698.degree. F., to form an energy fortified diesel fuel.