Hi Doc.
I thought that I would contact you again after reading the attached article entitled The Deadly Diesel Deception which was published in the Daily Mail on Thursday 1st May. A lot of the author’s points in relation to soot emissions are (unfortunately) correct when considering the older diesel vehicles, but surely vehicles built to Euro 4 standards, as well as Euro 5 & 6, no longer emit the dangerous particles of which the writer complained? If you notice the tail pipes of diesel cars produced in the past four to five years, you will be hard pressed to notice any soot staining. Contrast this with modern petrol engine cars, the tail pipes of which are always black – suggesting much higher soot emissions than current diesel vehicles. In addition, diesel emissions are falling rapidly to (almost) petrol engine levels, so I don’t see how modern emission controlled diesel engines are more dangerous for the health of people than current petrol cars? I understand that Euro 6 standards allow diesel vehicles to emit no more particles than petrol engines, and that the new breed of direct injection petrol engines will soon require fitment of Gasoline Particulate Filters to ensure compliance with emissions standards. Would it not be a good idea for the Government to follow the German idea, and introduce financial incentives to persuade owners of older vehicles to retro-fit them with diesel particulate filters, such as the sintered metal type produced by HJS? see:
http://tinyurl.com/DocD-HJS-city or search for HJS City-Filter.
These filters won’t block up, and stop a high proportion of fine soot particles from entering the air. This would potentially help to remove or reduce a lot of the anti-diesel bias in the press now and give older cars, vans, lorries etc., a longer, cleaner lease of life, and help to clean up our air as a bonus. If the Government wanted to encourage use of such filters, they could, for example, give owners of DPF retro-fitted cars a two-year road tax holiday, plus reduced road tax from then on? Perhaps, Dear Doctor, you would like to send in a article to the Daily Mail refuting many of the inaccurate statements made by Mr Derbyshire, as our resident diesel expert?
Regards Danny G

Thanks Danny. I wasn’t in a mood to start trading words with The Daily Mail, and they usually don’t print things that don’t agree with their opinions anyway. But you make a very good point indeed about petrol engine tailpipes, and it makes me wonder if there’s perhaps some deception or degree of misinformation somewhere. I well remember sticking a paper tissue up the tailpipe of one of the early DPF cars and being amazed how (almost) clean it came out.
Doc