Coprocessing of coal with a petroleum waste containing grease in waste oil was studied. Experimental parameters such as temperature, pressure, reaction time, coal loading, and grease loading in the system were examined. Coal conversions were found to increase with temperature, hydrogen pressure, reaction time, and coal loading. Coal conversions in excess of 90% were obtained during coprocessing, with conversions to oil of over 50%. At a fixed coal loading, the presence of a higher amount of grease in the system was found to increase the conversion of coal. This can be explained as due to the catalytic action of the heavy metals such as molybdenum in the grease during coprocessing. The high aromaticity of waste grease made it a good solvent for coal liquefaction. The waste oil and waste grease were demetalized during coprocessing, and the viscosity of the oil was reduced.