Ethanol is considered as an alternative fuel for spark ignition engine because of its ability to reduce the air pollution and cost of the fuel. The purpose of this experimentation is to investigate the emission characteristics of a single cylinder four stroke petrol engine using ethanol–gasoline blended fuels with various blends (0%, 20%, 40%, 60%, 80% and 100%). Exhaust emissions were analyzed for CO, CO2, NOx and HC by using different ethanol gasoline blends on volume basis at 1/4 throttle and variable engine speed from 1000 to 4000 rpm. Results were compared with the pure gasoline. It showed that as the ethanol content in blend increases, HC and CO emission decreases as a result of the leaning effect caused by the ethanol addition whereas CO2 and NOx emission increases.