This invention relates to a lubricating oil composition comprising: at least 50 mass % or more of one or more base oils; detergent; and 0.01 to 20 mass % of a functionalized polymer comprising a partially or fully saturated olefin homopolymer or copolymer backbone and at least one functional group, having: i) an Mn of 10,000 g/mol or more (GPC-PS) of the polymer prior to functionalization, ii) where in the functional group is derived from an acylating agent and a compound containing amino and/or hydroxyl groups, and iii) optionally, wherein the homopolymer or copolymer backbone is derived from monomers selected from the group consisting of C2 to C30 (such as linear) alpha olefins and C4 to C20 conjugated dienes; where PIBSA-PAM having an Mn of 1,600 g/mol or more (GPC-PS) is absent or substantially absent from the lubricating oil composition, or, if present, is present in an amount such that the weight ratio of the functionalized polymer (B) to the high molecular weight PIBSA-PAM is at least 0.25:1.