Lubricants with a terpolymer made of diester, olefin and acrylate The invention relates to a lubricant comprising a terpolymer which comprises in polymerized forma diester selected from di(C4-C22 alkyl)ester of maleic acid, fumaric acid, 2-methylmaleic acid, 2,3-dimethylmaleic acid, 2-methylfumaric acid, 2,3-dimethylfumaric acid, or mixtures thereof, an olefin selected from C6-C40 alky-1-ene, and an acrylate selected from C4-C40 alkyl (meth)acrylate. The invention further relates to the terpolymer, a process for preparing the terpolymer comprising the step of polymerizing the diester, the olefin, and the acrylate; and to a method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant or with the terpolymer.