Mixtures of olefin-ester copolymer with polyolefin as viscosity modifier

A lubricant composition comprising

• (a) about 16 to about 84.5 percent by weight of an oil of lubricating viscosity having a kinematic viscosity at 100° C. of less than about 15 mm2/s which comprises a poly-α-olefin;
• and
• (b) about 12 to about 44 percent by weight of an esterified copolymer having a weight average molecular weight of about 5,000 to about 30,000, with a backbone comprising units derived from (i) an α-olefin monomer of at least about 10 to about 14 carbon atoms and (ii) maleic anhydride or derivative thereof, wherein the mole ratio of (i) α-olefin monomer to (ii) maleic anhydride or derivative thereof is about 0.8:1 to about 1.1:1, said copolymer further containing nitrogen functionality derived from reaction of said copolymer with an amine which comprises an imidazolidinone, said copolymer containing about 0.075 to about 0.25 weight percent nitrogen;
• and
• (c) about 0.3 to about 25 percent by weight of a polyisobutene having a kinematic viscosity at 100° C. of at least about 1000 mm2/s and a weight average molecular weight of about 1,000 to about 3,000;
• wherein the polymers (b) and (c) are present in a weight ratio (b):(c) of about 6:4 to about 9:1 and wherein the total amount of polymer (b) plus (c) is about 25 to about 50 percent by weight of the lubricant composition.