Comparative experiments were conducted on a port injection gasoline engine fueled with hydrous ethanol gasoline (E10W), ethanol gasoline (E10) and pure gasoline (E0). The effects of the engine loads and the additions of ethanol and water on combustion and emission characteristics were analyzed deeply. According to the experimental results, compared with E0, E10W showed higher peak in-cylinder pressure at high load. Increases in peak heat release rates were observed for E10W fuel at all the operating conditions. The usage of E10W increased NO _X emissions at a wide load range. However, at low load conditions, E10W reduced HC, CO and CO₂ emissions significantly. E10W also produced slightly less HC and CO emissions, while CO₂ emissions were not significantly affected at higher operating points. Compared with E10, E10W showed higher peak in-cylinder pressures and peak heat release rates at the tested operating conditions. In addition, decreases in NO _X emissions were observed for E10W from 5 Nm to 100 Nm, while HC, CO and CO₂ emissions were slightly higher at low and medium load conditions. From the results, it can be concluded that E10W fuel can be regarded as a potential alternative fuel for gasoline engine applications.