A method of recovering oil from oil-based sludge including the steps of homogenizing an oil-rich phase, a water-rich phase, and a solids-rich phase of an oil-based sludge, removing particulates from the oil-based sludge as the sludge traverses a shaker screen, heating the sludge, injecting a chemical into the heated sludge and mixing the chemical with the heated sludge, separating the phases of the chemically-treated sludge into a solids component stream, a water component stream, a first oil component stream, and a gas component stream, removing solids from the first oil component stream with a decanting centrifuge to form a second oil component stream, and removing water and solids from the second oil component stream with a disk stack centrifuge.