In order to improve cold flow properties of palm oil biodiesel, varying the types of alcohol used at transesterification was examined. The pour point of palm oil biodiesel decreases as the carbon number of alcohol increases to 4. The pour point of palm oil isobutyl ester (PiBE) is lowest, 0°C, among 10 ester fuels made from different alcohols. The pour point of palm oil butyl ester (PBE) is 5°C, low for the second. Furthermore, PiBE, PBE, palm oil methyl, ethyl and propyl esters, rapeseed oil methyl ester (RME) and JIS No.2 diesel fuel (gas oil) were tested using a DI diesel engine. PBE and PiBE have the same thermal efficiency and NOx emissions compared to the other test fuels. HC, CO and Smoke emissions of palm oil ester fuels slightly increase when the carbon number increases. However, most of these exhaust emissions are lower than that of RME and the gas oil. From the experimental results, it is concluded that PBE and PiBE are good alternative diesel fuels.