New technology and innovative Fiat car parts have helped the car maker record the lower level of CO2 emissions than any other auto maker operating in Europe for the fifth year running.
According to the study by automotive research firm JATO Dynamics, the average CO2 output of Fiat branded vehicles sold in Europe in 2011 was 118.2 g/km, lower than any other brand and an improvement of 4.9 g/km on its average emissions in 2010.
It is the fifth consecutive time Fiat has ranked top in the study, during which time average CO2 output has been reduced by 14 per cent.
Fiat put its success down to the development of new technology and car parts which have helped make its vehicles increasingly efficient over recent years.
It cited the new TwinAir engine, which it claims is the world's most ecological turbo petrol engine, the use of alternative fuels such as methane to power its cars.