Industry analyst group Clean Green Cars has released its comprehensive list of CO2 emissions by manufacturer. The list tracks emissions every maker on the United Kingdom market and compares that data with past performance. Jeep and Subaru topped the list of most improved since Q1 2007, with BMW and Mazda following close behind.

The real success story was Jeep, improving its CO2 emissions by 21.01% over 2007 levels, reducing average CO2 output from 275.35g/km to 217.51g/km. Subaru was next closest, but still a considerable distance back at 11.36% improvement with reductions of 26.39g/km CO2 to an average of 205.95.

BMW followed at 10.96% improvement, although its Q1 2007 levels were below the final levels of the top two, so its improvement is all the more impressive, ending up at 163.38g/km CO2. BMW’s Mini brand also saw reductions of 10.77%, bringing it to a scant 138.87g/km CO2 average. Mazda rounded out the top five most improved brands with its 9.27% reduction to 166.89g/km CO2.

Chevrolet, Saab, Kia and Vauxhall were among the least improved, each actually worsening their fleet average CO2 scores compared to a year ago. Chevrolet managed an increase in emissions of 7.47%, rising from 160.37 to 172.35g/km CO2. Saab, Kia and Vauxhall’s gains were much smaller, at 0.03%, 0.25% and 0.21% respectively, meaning each maker effectively maintained emissions equivalent to 2007 levels.

As car makers continue to push the envelope of ‘green’ technology, reducing emissions and improving fuel economy, one has to wonder where the point of diminishing returns is reached. Increased research and development costs, increased production costs and increased government taxation are all leading to ever more expensive cars. Nevertheless, the fossil fuel-powered automobile industry appears to have long legs indeed - and with year-on-year improvements like these, it seems the end isn’t as near as many would have thought.