One important development area for better fuel economy is to reduce mechanical friction losses in engine components. Especially the friction reduction of piston assembly of which account for 30-50% of total engine friction is significantly effective method. This paper describes the friction reduction effect of DLC(diamond-like carbon) coatings and ZALC(ZrAlCu) coatings at the piston pin and rings by engine test. In the case of DLC and ZALC coating pin, the friction torque was decreased at all engine speed and the friction reduction effect was good at low oil temperature condition. In the case of DLC and ZALC coating rings, the friction torque was decreased at high engine speed but the friction torque was increased at low engine speed. Test results show that ZALC coating is more effective than DLC coating by 2%.