This study investigated the performance and emissions of a diesel engine fueled with corn oil methyl ester (COME) biodiesel that was preheated to different temperatures. COME was produced via transesterification of corn oil with methanol and tested in a single cylinder diesel engine. The viscosity of COME and its blends with diesel decreased with increasing preheat temperature up to 70°C. Testing found that preheating COME to 70°C improved brake thermal efficiency and reduced CO and HC emissions compared to diesel, but increased NOx emissions. Higher preheat temperatures like 90°C decreased performance due to vapor locking. Overall, preheating COME to 70°C allowed it to be used as a viable diesel alternative