Diesel oxidation catalyst and exhaust system

An oxidation catalyst for treating an exhaust gas from a diesel engine, which oxidation catalyst comprises:

• a flow-through substrate having an inlet end and an outlet end and a total length therebetween;
• a first washcoat zone disposed directly on to a surface of the substrate at an inlet end of the substrate and having a length that is less than the total length of the substrate, the first washcoat zone comprising platinum (Pt), palladium (Pd), manganese (Mn) and a first support material;
• a second washcoat zone disposed directly on to the substrate at an outlet end of the substrate and having a length that is less than the total length of the substrate, the second washcoat region comprising a platinum group metal (PGM) which is platinum (Pt) or a combination of platinum (Pt) and palladium (Pd), a zeolite, manganese (Mn) and a second support material;
• and
• a third washcoat zone disposed on the first washcoat zone and having a length that is less than the total length of the substrate, the third washcoat zone comprising a zeolite catalyst, the zeolite catalyst comprising a noble metal, which is palladium (Pd) and/or platinum (Pt), and a zeolite,
• wherein the second washcoat zone is in contact with the first washcoat zone and the second washcoat zone is arranged to contact the exhaust gas at the outlet end of the substrate and after contact of the exhaust gas with the first washcoat zone,
• wherein the first washcoat zone is substantially free of a zeolite, and
• wherein the first washcoat zone and the second washcoat zone have different compositions.