ABSTRACT An experimental study was carried out to investigate the effects of gasoline/diesel blended fuels on engine performances based on an inter-cooled, common rail, four-cylinder diesel engine. Tests were executed at a constant engine speed of 1800 r/min and different loads of 3.2 bar, 5.1 bar, 7.2 bar Indicated Mean Effective Pressure. The influences of several key boundary parameters including the gasoline fraction, the EGR ratio and the injection parameters were examined and discussed. The test results show that with the increase of the gasoline fraction within the fuel, the ignition delay is prolonged with the combustion duration being extended. It also leads to an increased proportion of premixed combustion in constant volume and a decreased smoke opacity level. However, excessive gasoline degrades the fuel economy especially under low loads, but this can be recovered to a certain extent by a carefully control of combustion phasing achieved through the fuel injection timing adjustment and an optimum combustion phasing is identified. In addition, comparing to the pure diesel, the gasoline/diesel blended fuel is more compatible to higher EGR ratios; and this makes it possible to reduce the NOx emission by applying larger EGR, without requiring high injection pressure. The effects of the coupling control strategy of using larger EGR, together with blends of a high gasoline fraction can be confirmed effective, in regards to the simultaneous reduction of NOx and PM. Given the combustion phasing and injection pressure to be controlled reasonably, almost no penalty will be imposed on the engine efficiency.