Ethanol has been used as an alternative fuel or fuel addicts in spark ignition (SI) engines for years. However, the existing methods of using ethanol fuel, such as blending gasoline and ethanol, pure ethanol and by-fuel of ethanol or gasoline do not make the best use of ethanol's potentials in improving engine performance. Compared with gasoline fuel, ethanol fuel possesses greater octane number and latent heat of vaporization, which allow higher compression ratio and consequently lead to the increased thermal efficiency. Ethanol fuel's higher combustion velocity could also help increase the combustion efficiency and minimize the energy loss. This paper reports our preliminary investigation to the leveraging effect of using ethanol direct injection plus gasoline port injection (EDI + GPI) on reducing the consumption of gasoline fuel. Experiments were conducted on a YBR250 engine which was a single cylinder SI engine modified to be equipped with EDI + GPI. At each of the four designated engine speeds, the engine load was set to be either medium or light and the ethanol/gasoline energy ratio (EER) was varied from 0% to 60.1%. The rate of the total heating energy of two fuels was kept constant in one of the two engine load conditions. Experimental results were analyzed and discussed in terms of engine performance, in-cylinder combustion characteristics and engine emissions. They showed certain leveraging effect of using ethanol fuel by the increased BMEP, volumetric efficiency and thermal efficiency and reduced NO with the increase of EER. (C) 2012 Elsevier Ltd. All rights reserved.