The objective of the present study is to reveal the effects of pure coconut oil and coconut oil-diesel fuel blends on the performance and emissions of a direct injection diesel engine. Operation of the test engine with pure coconut oil and coconut oil-diesel fuel blends for a wide range of engine load conditions was shown to be successful even without engine modifications. It was also shown that increasing the amount of coconut oil in the coconut oil-diesel fuel blend resulted in lower smoke and NOx emissions. However, this resulted in an increase in the BSFC. This was attributed to the lower hearing value of neat coconut oil fuel compared to diesel fuel. (C) 2001 Elsevier Science Ltd. All rights reserved.