Abstract: A method of reconstituting used cooking oil which includes the steps of gravity separation of constituents of high specific gravity under elevated temperatures and preferably a light vacuum, decanting the cleared oil, then without artificially-induced heating or cooling, passing the decanted oil through a fibrous filter such as, for instance, a string-wound or other cartridge-type filter and subsequently passing the oil through a Fuller's Earth (or equivalent) cartridge-type filter, thereafter adding a quantity of finely-divided bleaching clay to the filtered oil, further elevating the temperature and holding the mixture in a sterilizable container at the elevated temperature while agitating it, adding saturated steam and maintaining a vacuum for a period of approximately one-half hour, then cooling and filtering the mixture into a vacuumized atmosphere to remove the clay, and then cooling the filtered oil to a handling temperature and filling it into suitable containers for marketing it.