Polymer combination useful in fuel oil to improve cold flow properties

Claim 1

A fuel composition comprising a fuel consisting of wax-containing middle distillate pertroleum light fuel oil boiling in the range of 250° to 900° F., having a viscosity of 1.6 to 7.5 centistokes at 100° F., having less than 1 wt. %, based on the total weight of the fuel, of n-paraffin wax boiling above 350° C., and of which at least 5 wt. % of said oil boils above 700° F. according to ASTM-D-1160, which oil has been improved in its low temperature flow properties, said oil containing in the range of about 0.005 to 0.1 wt. %, based on the weight of the total composition, of a synergistic flow improving combination of one part by weight of an oil soluble ethylene backbone middle distillate pour point depressing polymer having a number average molecular weight in the range of about 1000 to 6000 per (b) 0.2 to 4 parts by weight of a second oil soluble polymer having a number average molecular weight in the range of about 1000 to 100,000; wherein said ethylene backbone polymer is selected from the group consisting of branched polyethylene, and copolymers consisting essentially of 4 to 20 molar proportions of ethylene with a molar proportion of ethylenically unsaturated alkyl ester of the formula: ##STR4## wherein R 1 is hydrogen or methyl; R 2 is a --OOCR 4 or --COOR 4 group wherein R 4 is a C 1 to C 4 alkyl group, and R 3 is hydrogen, and mixtures of said comonomers, and wherein said second polymer is a polymer selected from the group consisting of: (a) ester copolymers consisting of dialkyl fumarate copolymerized with 5 to 70 mole % of a comonomer selected from the group consisting of vinyl acetate and alkyl methacrylate, wherein said alkyl groups of said fumarate and said methacrylate consist essentially of C 6 to C 16 straight chain alkyl groups; and (b) polymers consisting essentially of C 8 to C 18 alpha monoolefin moieties.