This study discusses the effects of addition of small amount of ethanol on performance and emission behaviour of a gasoline fuelled lean burn SI engine. Experiments were carried out in a single cylinder diesel engine which is made to operate as SI engine on lean condition with gasoline as a fuel. The engine was operated at wide open throttle at a compression ratio of 10.5:1 and 1500 rpm at diverse equivalent ratios by injecting the fuel into manifold. The test outcomes stipulated that use of ethanol-gasoline blend (10% by volume) was better compared with pure gasoline. The test results also revealed that there was an accountable increase in brake power output, brake thermal efficiency and an apparent extension in the lean limit of operation with ethanol-gasoline blend. In emission front, reduction in hydrocarbon and carbon monoxide emissions were observed. There was an increase in carbon dioxide and NO emissions due to better combustion and high in-cylinder temperature. On the whole it is concluded that small ethanol addition to gasoline improves performance and reduces emission for lean operating SI engine. © 2019 Published under licence by IOP Publishing Ltd.