Ethanol fuel is a sustainable energy resource that is intended to provide a more environmentally and economically friendly alternative to petroleum-based fuels, such as gasoline. Recent interest in ethanol has increased due to the fact that it can be combined with gasoline at different percentages: from low percentages with not specially modified gasoline vehicles up to 85% of ethanol, and even up to 100%, in flexible-fuel vehicles.There is much debate and a considerable amount of concern among automakers and consumers regarding the environmental friendliness of ethanol, mainly due to the lack of complete knowledge about the effects of its use on direct pollutants from exhaust vehicle emissions such as CO, CO₂, NOx, HCs and particulates and on the fuel consumption of the vehicle. Furthermore, there is concern regarding the impact that ethanol could have on the different VOC's, principally because they are ozone precursors due to their reaction in the atmosphere with nitrogen oxides (NOx) in the presence of sunlight, which contributes to ground-level ozone formation.This paper aims to evaluate the impact of adding ethanol to gasoline on exhaust emissions and fuel consumption, measuring regulated and non-regulated pollutants. To achieve this objective, exhaust emissions tests adapted to the use of ethanol blends were performed using a Euro 4 vehicle running with E0, E5 splash and E10 and a flexible-fuel vehicle running with E0 and E85. An analysis of the automotive engine exhaust for standard pollutants (CO, CO₂ HC, NOx, particulates) was performed. Then these regulated measurements were completed with the speciation of the exhaust emissions determining the different contributions of some aldehydes, ketones, ethanol and different individual hydrocarbons, determined by HRGC-FID and HPLC-UV. This long list of pollutants and their particular ozone-forming potential were used to estimate ground-level ozone formation and the effect of different ethanol-gasoline blends on it.The paper concludes with an evaluation of the results obtained in order to determine the effects of adding different percentages of ethanol to gasoline on exhaust emissions (regulated and non-regulated) and fuel consumption as well as to determine the impact on ground-level ozone formation.