In this study, methyl ester produced from waste frying oil based palm-oil was used as an alternative diesel fuel in a four-cylinder, naturally aspirated, indirect injection (IDI) diesel engine. Obtained engine test results were compared with reference values which were determined by using petroleum-based diesel fuel (PBDF). In order to determine the engine performance and emission levels, the engine was exposed with full load-varied speed tests. The test results showed that when methyl ester was used, the brake specific fuel consumption increased slightly, while the brake torque and power decreased by comparing to petroleum-based diesel fuel. In the experiments, carbon monoxide (CO), carbon dioxide (CO(2)), unburned hydrocarbon (HC), nitrogen oxides (NO(x)) and smoke opacity values has been measured for each fuel. Emission results showed that the methyl ester has provided significant reduction in HC, CO and smoke opacity emissions. But, by using the methyl ester, the NO(x) emissions have increased compared to PBDF.