Sir – As an ex-Vauxhall employee I’ve always regarded car manufacturer’s performance claims with a pinch of salt, though VW’s software cover-up was a bit of a novelty.

I have a diesel car so should I feel bad about it?

Unfortunately, the answer is far from simple. Diesel engines produce less CO2 per mile than petrol engines but more NOX. CO2 is bad for the environment, NOX bad for humans. However, NOX is beneficial for trees which take in CO2 and give out oxygen which is good.

VW’s solution is fitting new exhausts that are more expensive to make and run but chemically removes more NOX. We could also do this for all diesel engines and not pillory VW as being the only bad guy on the block.

Terry Randall
Grove Street
Wantage