But the report on the emissions of the cars on Brazil's roads did not count carbon dioxide emissions.
"We want to make sure that customers are aware of pollutant emissions when they buy a car," said Brazilian Environment Minister, Mr Carlos Minc.
The study ranked emissions based of a scale of "green grades'' that measured three pollutant gases that did not produce climate change but did affect the health of a country's population: carbon monoxide, hydrocarbons and nitrogen oxide.
The green grade scale, ranging from 0 to 10, did not count carbon emissions, which were the main driver of global warming, because emissions from burning ethanol were offset by the carbon dioxide that sugar cane absorbed as it grew, the study said.
The research also examined 250 "flex-fuel'' cars, which used both ethanol and petrol and constituted about 85 per cent of all cars on the road in Brazil.
Among those receiving the lowest scores, eight were cars running on ethanol, including several with "flex'' engines, the study said, though all of the models examined met Brazil's standards for maximum emissions levels in 2008.
Environmental group Greenpeace welcomed the report, but an official with the group's climate change campaign in Brazil, Joao Talochhi said, "when it comes to public health, the Brazilian Government should invest in non-polluting vehicle technology".