The use of ethanol/gasoline blends on gasoline engines is not only a potential solution for satisfying the fuel demand but also for reducing emissions from vehicles which cause environmental pollution and adverse health effect. In Vietnam, the blend with 5% of ethanol (E5) has been widely used. However, blends with higher than 5% of ethanol should be studied and applied in order to improve the ability to substitute for gasoline. This paper presents the experimental results of in-use carbureted and fuel injected passenger cars fueled by gasoline RON92, E10, E15 and E20. These cars were tested at the steady state as well as following the ECE15+EUDC driving cycle. Results indicated the different influence of these ethanol/gasoline blends on power, fuel consumption and emissions of the cars.