The object of this study was to observe the combined effects of biodiesel and a IOW heat rejection combustion technique. To investigate the effect of biodiesel usage in a low heat rejection diesel engine, a direct injected, turbocharged diesel engine's cylinder head, valves, and pistons were coated with 0.15 mm of nickel-chrome-aluminum bond coat and 0.35 nun of yttria-stabilized zirconia. According to the engine tests, it was determined that brake specific fuel consumption was increased with biodiesel usage and low heat rejection application but decreased for low heat rejection diesel at low speed. Exhaust gas temperature, excess air ratio, and smoke absorption coefficient were decreased with biodiesel usage but increased with low heat rejection application. NOx emission was increased at low speed but decreased at high speed with biodiesel usage and it was increased with low heat rejection application.