Carboxylate-vinyl ester copolymer blend compositions for lubricating oil flow improvement

Compositions for improving at least the low temperature flow properties of high viscosity index, high saturates, low sulfur lubricating oils (also known as American Petroleum Institute Group II and Group III oils). The compositions comprise a mixture of lubricating oil flow improvers (LOFIs) that are specified first and second component copolymers of unsaturated dicarboxy esters, including a first component which is a polymer or copolymer of a carboxylate containing pendent ester groups wherein the average side chain carbon number is between 11.0 and 12.4, such as dialkyl fumarate/vinyl acetate copolymer, and a second component which also is a polymer or copolymer such as dialkyl fumarate/vinyl acetate copolymer, but wherein the average side chain carbon number is between 12.7 and 15.0. Alternatively, each of the polymers or copolymers can be esterified styrene/maleic anhydride copolymer, or esterified olefin/maleic anhydride copolymer provided that each of the two components has the specified, different average side chain carbon numbers.