Reducing agent metering device

Reductant dosing device comprises a reductant tank (3) and a supply line (5) connecting the tank with the exhaust gas pipe of the engine. The supply line is arranged in heat conducting contact with the fuel return pipe (12). Preferred Features: The reductant tank and the fuel tank (4) are arranged next to each other and the supply line is in heat conducting contact with the fuel return line over its whole length. The supply line is connected to a dosing valve (6) connected to the engine. The valve is connected on the outlet side via a feed line (7) subjected to pressurized air and connecting the valve to the exhaust gas pipe. The reductant is an aqueous urea solution.