Some manufacturers are progressing more than others in the race to reduce pollution from vehicle exhausts.
The latest round of testing by environmental assessment firm EcoTest has reported varying successes in cutting the emissions of CO2 and other pollutants from new cars.
Several cars achieved the highest score yet achieved – four out of five stars – for reducing pollutants according to the type of car.
These included the highest-scoring car in the latest batch of tests, the Mazda6 2.0 diesel estate, as well as the Volvo V50 1.6D, the Mercedes SL350 and the Citroën C5 Tourer HDi.
No car has yet achieved five stars.
At the bottom of the table was BMW’s M3 Cabriolet and Coupé, which scored very poorly for CO2 emissions although fared better when nitrogen oxides, hydrocarbons and carbon monoxide were taken into account.
EcoTest, which was set up by the FIA Foundation, said this shows the difficulties manu-facturers can have in addressing both pollutants and CO2 at the same time.
The ratings work by attributing points to cars.
To achieve a five-star rating, a car needs to score 90 points.
So far, the highest score has gone to the Toyota Prius
The Mazda6 scored 81.
The M3 Cabriolet scored zero.
Other poor performers included the Alfa Romeo Brera 2.4 JTDM, which achieved 11 points for CO2 emissions, the Mitsubishi Shogun 3.2 DI-D automatic, which scored 10 points and the Chevrolet Captiva 2.0 LT Sport (seven seat) with 15.
Sheila Watson, the FIA Foundation’s director of environment, said: “Manufacturers have been focusing much attention on producing greener cars and this is to be welcomed.
“However, the car industry now needs to reach the next level.
"This is a tough challenge, but the best performers are those that tackle both CO2 emissions and exhaust pollutants at the same time, and that is the standard which all manufacturers must aim for across all of their models.”