A novel highly grafted, functionalized olefin polymer is provided comprising the reaction product of a method comprising reacting an acylating agent with a mixture comprising an olefin polymer having a number average molecular weight of between about 5,000 to about 100,000 and a diluent in the presence of a free radical initiator to provide an acylated olefin polymer which is further reacted with a polyamine to provide the grafted functionalized olefin polymer dispersant. Lubricating oil concentrates and compositions containing the highly grafted, functionalized olefin polymer and uses thereof also are provided.