That means they are likely to reach European Union pollution targets ahead of time.
A new study said cars sold in the EU in 2009 on average emitted 5.1% less C02 than cars sold in 2008.
Brussels-based Transportation & Environment said that is the steepest annual reduction in emissions since the EU started collecting data 10 years ago.
Japanese manufacturer Toyota cut emissions by 10%, faster than any other car maker.
Car makers face EU fines if, by 2015, they fail to cut their fleets’ average CO2 emissions by 35% from 1995 levels.
CO2, like other greenhouse gases, has been linked to global warming and the EU has committed itself to cut its total greenhouse gas emissions by at least 8% between 2008 and 2012. The European Environment Agency estimates that cars are responsible for about 14% of the EU’s total CO2 emissions.
There are two main reasons for last year’s record reduction, said Transportation & Environment.
The economic crisis – together with cash incentives to scrap old vehicles and replace them with newer ones in many EU member states – lifted demand for cheaper and smaller, and thus usually more fuel-efficient, cars.
However, the report said, better technology was responsible for more than half of the cut in emissions, suggesting that the 2009 figures shouldn’t have come as a big surprise for the car industry.