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In Brazilian market, Flex-Fuel vehicles represented over 85% of new light-duty vehicles sold in 2010. These vehicles can use gasoline blended with anhydrous ethanol (18 to 25% v/v), 100% of hydrous ethanol (contains from 6,2 to 7,4% w/w of water) or any blend of these fuels. Some studies regarding Flex-Fuel technology are being made in Brazil, but there are not many published information about fuel properties of different ethanol-gasoline blends. Also, it is important to better understand emissions of aldehydes, unburned ethanol and total hydrocarbons of different ethanol blends on gasoline. A Flex-Fuel engine, 1.4 l, 4 cylinders was tested on a dynamometer. A FTIR (Fourier Transform Infrared analyzer) bench measured aldehydes, unburned ethanol and total hydrocarbons. It was used Gasoline with 25% of anhydrous ethanol was used as a reference fuel (E25). E25 was blended with different hydrous ethanol contents such as 30% (H30), 50% (H50), 80% (H80) and 100% (H100).

The secondary pollutants formation in the atmosphere, such as ozone (O3), comes from the reactions between volatile organic compounds (VOCs) and the photochemical oxidants in the presence of oxygen and nitrogen oxides (NOx). The understanding of VOCs reactivity emitted by light duty vehicles is very important to construct reactivity scales regarding ozone formation. In 2003, flex-fuel vehicles were released in the Brazilian market and nowadays, they represent over 50% of the total light duty vehicle fleet in the country. In 2007, new tailpipe emission limits were implemented for Non-Methane Hydrocarbons (NMHC), a group of pollutants included in VOCs. The new NMHC limit became a challenge to homologate some flex-fuel models, when fueled with ethanol. To deal with this issue, other legislation allowed the subtraction of the unburned ethanol emission from the NMHC value.