Abstract: An oil sludge mixing assembly replaces a screw driven oil sludge separator with a hydraulic mixing assembly. The assembly includes a chamber configured to hold a mixture comprising oil, water, and sludge in the interior space. An inlet is coupled to and extends into the chamber wherein the inlet is configured for passing the mixture into the interior space of the chamber. An outlet is coupled to and extends through the chamber wherein the outlet is configured for passing the mixture out of the interior space of the chamber. A housing is coupled to the chamber and an arm is extendably coupled to the housing. A paddle is coupled to the extendable arm such that the paddle is moved within the interior space by the arm for agitating the mixture in the interior space of the chamber and directing settled sludge to the outlet.