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In order to utilize tung oil as an alternative diesel fuel, the combustion characteristics and exhaust emissions of tung oil methyl ester (TME) were investigated by using a single cylinder DI diesel engine. Also the comparisons were carried out on combustion characteristics and exhaust emissions of TME with rapeseed oil methyl ester (RME) and JIS No.2 diesel fuel (gas oil). From the experimental results, the stable engine operation was achieved by fuelling TME as those of RME and the gas oil. The thermal efficiency of TME is almost the same as that of the gas oil. TME has longer ignition delay compared to the other test fuels due to the lower ignition ability. The pour point of TME is -7.5°C and that is the same as that of RME. The exhaust emissions (HC, CO, NOx and smoke) of TME are higher than those of RME and the gas oil. From the experimental results, it is necessary to improve the fuel properties of TME for better diesel combustion.

In order to improve the cold flow properties of coconut oil biodiesel and to reduce the lifecycle CO2 emission by using bio-alcohol at biodiesel manufacturing, varying the types of alcohol used at transesterification was examined. The pour point of coconut oil ester decreases as the carbon number of alcohol increases. Among 5 ester fuels, the pour point of coconut oil isobutyl ester (CiBE) made from isobutanol is lowest, −12.5 °C, compared to that of coconut oil methyl ester (CME), highest, −5 °C. The pour point of coconut oil 1-butyl ester (CBE) is −10 °C, second lowest. Furthermore, CBE, CiBE, CME and JIS No.2 diesel fuel (gas oil) were tested using a DI diesel engine. CBE and CiBE have shorter ignition delay compared to the gas oil although slightly longer than CME. CBE and CiBE have the same thermal efficiency and NOx emissions compared to the gas oil. HC, CO and Smoke emissions of coconut oil ester fuels slightly increase when the ester molecule carbon number increases.