This study was focused on fuel energy efficiency and pollution analysis of different ratios of ethanol-gasoline blended fuels (E0, E3, E6, and E9) under different loadings. In this research, the experimental system consisted of a small engine generator, a particulate matter measurement system, and an exhaust gas analyzer system. Different fuels, unleaded gasoline, and ethanol-gasoline blends (E0, E3, E6, and E9) were used to study their effects on the exhaust gas emission and were expressed as thermal efficiency of the small engine generator energy efficiency. The results suggested that particle number concentration increased as the engine loading increased; however, it decreased as the ethanol content in the blend increased. While using E6 as fuel, the carbon monoxide (CO) concentration was less than other fuels (E0, E3, and E9) for each engine loading. The average of CO concentration reduction by using E3, E6, and E9 is 42, 86, and 83%, respectively. Using an ethanol-gasoline blend led to a significant reduction in exhaust emissions by approximately 78.7, 97.5, and 89.46% of the mean average values of hydrocarbons (HCs) with E3, E6, and E9 fuels, respectively, for all engine loadings. Using an ethanol-gasoline blend led to a significant reduction in exhaust emissions by approximately 35, 86, and 77% of the mean average values of nitrogen oxides (NO x ) with E3, E6, and E9 fuels, respectively, at each engine loading. The E6 fuel gave the best results of the exhaust emissions, and the E9 fuel gave the best results of the particle emissions and engine performance. The thermal efficiency of the small engine generator increased as the ethanol content in the blend increased and as the engine loading increased. INTRODUCTIONWith higher scale of consumption of nonrenewable fuels, the quest for an appropriate alternative fuel has gathered great momentum. The consequence to reduce pollutant emissions from petroleum-based engines has actuated the development and testing of several alternative fuels in recent years.Alcohols (e.g., ethanol, which is a colorless liquid with mild characteristic odor and can be produced from coal, natural gas, and biomass) have a high octane number and can be used as one of the practical alternative fuels. Furthermore, ethanol has a higher heat of vaporization than gasoline, which means it freezes the air, allows more mass to be drawn into the cylinder, and increases the power output. In addition, ethanol has antiknock characteristics that improve engine efficiency and give higher compression ratios.Ethanol contains an oxygen atom; therefore, it can be regarded as a partially oxidized fuel. 1,2 Because of this, it has a lower heating value and stoichiometric fuel-to-air ratio than gasoline. As a result, much more fuel is needed to obtain the same performance when ethanol or ethanolgasoline blends are used. 1,3,4 Ethanol has a higher octane number than gasoline, thus it can lead to operation at higher compression ratios and therefore improvement in power output, efficiency, and fuel con...