Performance characteristics; brake thermal efficiency (BTE), Specific fuel consumption (SFC), fuel power (FP) and brake power (BP) of  blended(gasoline/bio-ethanol) fuels were studied and compared with neat gasoline fuel. These blends were namely; E05, E10, E15 and E20.The performance parameters were measured based on successful completion of engine standard short tests carried out on a Cortina petrol engine test bed, a four stroke engine, and variable speed SI engine with eddy current dynamometer and Tachometer. The result showed that E05 and E10 were the optimum blending ratios for bioethanol and gasoline. It can be concluded from these results that E05 and E10 are the most suitable blends for use in four stroke SI engines.