system for recovering purified oil from a mixture of oil , water , and solid particles ; comprising allowing the mixture to settle while heating to about 160 ° f . to form a lower water layer and an upper oil layer ; pumping off the water layer and passing it through a strainer to separate solids ; pumping off the oil , passing it through a strainer to remove solids , heating the strained oil and passing it through a purification step including filtering fine solids , heating the oil to vaporize any volatile components , and separating the vapors so produced .