We have worked on the fuel expenses reduction of the fuel melting furnace. We are developing two methods as the running reduction method. They are the method of mixing the combustible such as waste plastics with the being melted waste and the method of the conversion and the addition to another fuel. We report about the result of combustible mixing test at the real operation plant (Waste Treatment Center in Yokkaichi City, Mie Prefecture) and the fuel expenses decrease trial calculation result based on the test result.