Neither petrol nor diesel vehicles are particular environmentally friendly. However there has been a growing drive to promote the use of diesel vehicles as environmentally less damaging, as they tend to have lower CO2 emissions. This is important as CO2 is one of the major greenhouse gases driving climate change.

However this does not take account of the relative performances when it comes to local air quality. The air quality in many parts of Merseyside is poor and within parts of Liverpool the levels of NOx exceed government targets. It is therefore important to strike a balance between tackling global warming and local air quality problems. To find out more about the pollutants that cause poor air quality, what effect they are having on your health and how Liverpool City Council plans to improve air quality, click here.

If we take an average of all of the petrol cars and all of the diesel cars on sale today the average petrol car produces 214g/km of CO2 whilst the average diesel produces just 169g/km of CO2. However this tends to under estimate the performance of petrol vehicles as high performance (and therefore high CO2 emitting vehicles) are petrol not diesel.

Within each class the differences are often far less clear cut as is the case with the lowest CO2 petrol and diesel vehicles currently available (Jan 2007):

Whilst there is no difference in CO2 emissions they perform very differently in terms of the emissions that cause poor local air quality:

Despite using a very clean modern diesel engine, the diesel’s produce  24 times more NOx than the petrol versions and produce particulate matter which the petrol does not. The petrol does however produce twice the amount of carbon monoxide.

If you are prepared to consider a hybrid car the gains can be even greater and potentially from a far larger car:

If you are considering buying a new vehicle please consider alternative fuels. However if you still decide to buy a petrol or diesel vehicle make sure to ask for details of all of the pollutants, not just CO2!

To find out what your next car should be emitting in terms of CO2, NOx, PM and CO continue to the next section. If the car that you were considering doesn’t meet these standards please think again and tell your dealer why!