Recently, the environmental problems by the global warming have become more serious and fuel economy regulations of all over the country have been tightened. For these reason, the vehicle consumer’s concern about “environmental?friendly” and “higher fuel economy” have been higher every day. According this trend, new technologies for the higher fuel economy are developed actively by car makers of the world. This paper presents the technology for improving the fuel consumption by the wasted exhaust heat recovery system. Exhaust heat recovery system supply the heat energy of exhaust gas to engine coolant and auto transmission oil at low temperature right after engine starting. It reduces engine and auto transmission warm-up time, and reduces the power-train friction loss, therefore, it is possible that fuel consumption is improved. In this paper, the optimization of heat exchange efficiency for higher fuel economy is studied. And also, exhaust tail pipe noise & pressure drop is optimized for the total exhaust system performance.