Residue wax, also known as foots oil or microcrystalline wax, is a type of wax derived from the residual fraction of the petroleum refining process. It is produced as a byproduct of the dewaxing process used to remove wax from lubricating oil fractions. Residue wax differs from slack wax in that it contains a higher proportion of oil and heavier hydrocarbons, as well as impurities such as aromatics and resins.