The use of wet ethanol with higher water content than the conventionally used in internal combustion engines can reduce fuel production costs due to lower energy expense during the distillation phase. However, during its combustion the extra water content may result in the deterioration of fuel conversion efficiency and therefore a global energy evaluation should be considered. This research investigated the operation of a single cylinder direct injected spark ignition engine running with gasoline, anhydrous ethanol and several wet ethanol compositions (5-20% of water-in-ethanol volumetric content) under stoichiometric and lean air/fuel ratios. Two part load conditions of 3.1 bar and 6.1 bar indicated mean effective pressure were evaluated at 1500 RPM. The impacts of increased water-in-ethanol content and lean operation on combustion and emissions were discussed. Higher water content affected the heat release rate, which increased the combustion duration and initial flame development phase. Lower nitrogen oxides emissions could be achieved with higher water-content ethanol at the expense of higher unburned hydrocarbon emission. An analysis of wet ethanol energy production costs and engine operation conditions was carried out. The lean engine operation with 10% (v/v) water-in-ethanol fuel showed global energy savings around 31% compared to anhydrous ethanol at stoichiometric conditions. (C) 2016 Elsevier Ltd. All rights reserved.