Olefin-dicarboxylic anhydride copolymers and esters thereof are dewaxing aids

In a solvent dewaxing process for the separation of wax from a distillate lubricating oil fraction having about 5 to 30 weight percent wax, by the steps which include diluting the oil with solvent, chilling the diluted oil to a temperature in the range of -7.degree. C. to -40.degree. C. to form solid wax crystals and filtering to remove said wax crystals;

• the improvement which comprises incorporating into said oil prior to formation of said wax crystals a wax crystallization modifying amount of an oil-soluble dewaxing aid copolymer having a number average molecular weight in the range of about 1500 to 20,000, said copolymer consisting essentially of 1-olefin of 30 to 50 carbon atoms copolymerized in essentially equi-molar proportions with maleic anhydride.