A lubricating oil composition and methods of operating an internal combustion engine to provide improved engine operation. The lubricating composition includes a major amount of oil of lubricating viscosity; and a minor amount of at least one highly grafted, multi-functional olefin copolymer made by reacting an acylating agent with an olefin copolymer having a number average molecular weight greater than about 10,000 up to about 50,000 in the presence of a free radical initiator to provide an acylated olefin copolymer having a degree of grafting (DOG) of the acylating agent on the olefin copolymer of from above about 1.5 to about 3.0 wt. %. The acylated olefin copolymer is then reacted with an amine to provide the highly grafted, multi-functional olefin copolymer.