A lubricating oil composition comprising, or made by mixing, a major amount of an oil of lubricating viscosity and a minor amount of at least one compound comprising a polynuclear molybdenum core having bonded thereto one or more monoanionic ligands capable of rendering the compound oil-soluble or oil-dispersible, and further comprising at least one ionic species that is not required to confer oil-solubility or oil-dispersibility to the compound, wherein the combination of said one or more monoanionic ligands and said at least one ionic species confers electrical neutrality to the compound and wherein the ratio of the number of molybdenum atoms in the core to the number of said ligands is greater than 1:1.