Biodiesel is emerging as the promising choice for compression ignition engine due to its renewable, environmentally friendly and biodegradable nature, with superior emission characteristics. However, the true test of the suitability of biodiesel in a diesel engine lies with engine evaluated performance and emission test. This research work focused on the engine performance evaluation and emission test of gmelina seed oil fatty acid methyl ester (GSOFAME) or bidiesel on diesel engine. GSOFAME was produced using methanol and sodium hydroxide (NaOH) catalyst. The physiochemical property of the biodiesel was determined based on American standards for testing and materials (ASTM). The engine performance was carried out on Perkins 4:108 4 stroke diesel engine using GSOFAME, diesel and their blends. The fuel properties of the GSOFAME which are within the ASTM standard limits were determined as density 874kgm3 , kinematic viscosity 4.975mm2 s -1 at 400C, cetane number 64.2, flash point 1780C, cloud point 5 0C, pour point 30C, acid value 0.24mgKOHg-1 , calorific value 38.33MJ/Kg. The engine performance evaluation revealed that the BSFC of the blends decreased with increase in engine speed and attained minimum value at 1600rpm for B0-B40 and 1800rpm for B60-B100 and then started increasing with increase in speed. The BTH and BP increased with increase in engine speed and attained maximum values at1600rpm for B0-B40 and 1800rpm for B60-B100 and then started decreasing with increase in engine speed. Again the BSFC decreased with increase in engine load and attained minimum value at 70% of the maximum load or 70kg and then started increasing with increase in load. The BTH and BP increased with increase in engine load and peaked at 70% of the maximum load when they started decreasing with increase in load. The results showed that the BSFC, BTH and BP of B20 are close to that of B0. However the BTH of B20 and blends with less biodiesel fraction proved superior to that of B0 by exhibiting higher BTH. The engine emission test shows that CO, HC and NOx emission increased with increase in load for B0-B100. At a specific load, CO and HC decrease with increase biodiesel fraction while NOx emission increased with increase in biodiesel fraction. The overall result shows that B20 and blends with less biodiesel fraction can be used directly in a diesel engine without any engine modification. Again the low emission from GSOFAME shows that it will have minor negative impact on the environment

Keywords : Engine Emission Test, Engine Performance Test, Engine Load, GSOFAME, Transesterification