Two separate injectors were used to simultaneously inject ethanol and gasoline in the intake port of a single cylinder SI engine. The relative amounts of the two fuels on mass basis and the spark timing were changed using a real time controller. Neat gasoline could be used till 35% throttle beyond which higher thermal efficiency and torque could be obtained by switching to 30% ethanol. This system can be used to provide sufficient margin for knock free operation. Efficiency and torque were better at a mass ratio of 1:1 (50% of ethanol and 50% of gasoline) due to faster combustion as a result of better mixture preparation as compared to conventional pre-blended injection of gasoline and ethanol. However, NO and HC were slightly elevated. This dual injection system can allow the use of ethanol only when needed while permitting stoichiometric operation even under high torque conditions by adjusting the proportion of ethanol. Ethanol-gasoline and n-butanol gasoline were compared in terms of performance and emission with dual injection strategy. The amount of n-butanol has to be increased with increase in torque conditions for better performance and low emission. The benefit of using ethanol with gasoline is significant at high torque conditions. (C) 2016 Elsevier Ltd. All rights reserved.