In this study, the effect of ethanol-gasoline and methanol-gasoline blends on the engine performance and combustion characteristics has been investigated experimentally. In the experiments, a vehicle having a four-cylinder, four-stroke, multi-point injection system SI engine was used. The tests were performed on a chassis dynamometer while running the vehicle at two different vehicle speeds (80 km/h and 100 km/h), and four different wheel powers (5, 10, 15, and 20 kW). The measured emission values with the use of E5, E10, M5, and M10 have been compared to those of pure gasoline. The experimental results revealed that when the test engine was fueled with ethanol-gasoline or methanol-gasoline blends, CO, CO2, unburned HC and NOx emissions decreased for all wheel powers at the speed of 80 km/h. However, when the vehicle speed was changed to100 km/h, more complex trends occurred in the exhaust emissions for the fuel blends, especially for the wheel power of 15 kW. It was also seen that the air-fuel equivalence ratio increased with the increase of ethanol and methanol percentages in fuel blends when compared to pure gasoline case. (C) 2012 Elsevier Ltd. All rights reserved.