There is provided a diesel oxidation catalyst composition, wherein the composition comprises at least one non-noble metal oxide impregnated on a porous refractory oxide material of at least one platinum group metal and the fine particles in the form of impregnated on a porous refractory oxide material in particulate form, in which at least one porous refractory oxide material and at least one porous refractory oxide material impregnated with a non-noble metal oxide was impregnated with the platinum group metal in the form of a mixture or the at least one platinum group metal and at least one non-noble metal oxide is the same porous refractory It is impregnated in the oxide material. Diesel oxidation catalysts as well as the oxide does not damage relatively hydrocarbon provide synergistic enhancement of the oxidation of carbon monoxide. Preparation and use of the emission treatment system, and a catalyst composition comprising a catalyst article coated with the catalyst composition is also provided.