<div class="htmlview paragraph">This paper describes the development of new Si₃N₄ ceramics with both low friction coefficient and high strength, aiming at the reduction of friction force between cylinder liner and piston ring in low heat rejection engine.</div> <div class="htmlview paragraph">Si₃N₄ ceramics has high Young's modulus, therefore it provides lower coefficient of friction than iron. We thought that if adsorption ability of Si₃N₄ to lubricant oil were improved, coefficient of friction got still lower. In order to achieve this Fe₃O₄, which has superior adsorption ability, were used as one of additives for Si₃N₄. The obtained new Si₃N₄ had obviously lower coefficient of friction than conventional Si₃N₄ and it's strength were almost same as conventional Si₃N₄. Moreover, cylinder liner and piston ring were fabricated from developed Si₃N₄. They were tested using engine and reduction of friction force was confirmed.</div>