To improve combustion efficiency by activating moisture included in the intake air of an engine.

Only by making an infrared-ray radiating material contact with engine fuel, combustion efficiency can be improved. Namely, if a material radiating near a wave length of 3.0 to 3.8 in an infrared-ray range is made to contact with the fuel, a vibration period of a molecule in the fuel is changed from a basic state to an excited state. If the fuel is sent into the engine, the fuel contacts with moisture included in air in a cylinder. Therefore, the moisture contacting with the fuel is influenced by the molecule vibration of the fuel and resonated, thereby changing the molecule vibration of water from the basic state to the excited state to be activated. If activated, the combustion efficiency of the engine is improved, and fuel can be saved.