Lubricant for use in diesel engines

A method of dispersing soot produced by a lubricated diesel engine, comprising lubricating the engine with a lubricating oil composition comprising more than 75% by weight of lubricant base stock, from 0.1-2.5% by solids weight said functionalized of a graft reaction product of a monomer selected from the group consisting of N-vinyl imidazole, 1-vinyl-2-pyrrolidinone, N-allyl imidazole, 1-vinyl pyrrolidone, 2-vinyl pyridine, 4-vinyl pyridine, N-methyl-N-vinyl-acetamide, di-allyl formamide, N-methyl-N-allyl formamide, N-ethyl-N-allyl formamide, N-cyclohexyl-N-allyl-formamide, 4-methyl-5-vinyl thiazole, N-allyl-di-iso-octyl phenothiazine, 2-methyl-1-vinylimidazole, 3-methyl-1-vinylpyrazole, N-vinyl-purine, N-vinyl piperazines, N-vinyl succinimide, vinylpiperidines, vinylmorpholines, and combinations thereof grafted onto an ethylenic polymer backbone, said graft copolymer having a weight of from 20,000 to 500,00 and a polydispersivity of less than 10 and a molar proportion of grafted monomer to the final polymer of at least about 13:1, from 0-2.5% by solids weight of an ungrafted dispersant viscosity index improver, and from 0.2-less than 4% dispersant from a detergent inhibitor (D1) package, and optionally other additives aside from dispersants and viscosity index improvers;

• so as to effectively disperse soot produced by the diesel engine without adversely affecting the viscosity of the lubricant;
• and wherein the said lubricant composition comprises lubricant base oil, graft copolymer and ungrafted dispersant polymer.