A power system includes a dual fuel engine, a first fuel source configured to provide a first fuel to the engine, and a second fuel source configured to provide a second fuel to the engine different than the first fuel. The power system also includes an exhaust system configured to receive combustion exhaust from the engine. The exhaust system includes a reduction catalyst comprising palladium catalyst material and an oxidation catalyst comprising cobalt catalyst material. Additionally, changing a ratio of the first fuel provided to the engine relative to the second fuel changes a NOx conversion efficiency of the reduction catalyst.