Doctor Diesel

Diesel bashing again

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dd2diesel-bashing-againHello Doc

I’m sure that you’re as concerned as I am to have read phrases in the press recently like ìall diesels are illegalî and the like. I know that this is related to the real world tests that are going to be involved soon in testing for nitrogen oxide emissions, and I think that we all probably realise that something needs to be done in big city areas where the nitrogen oxide levels are often very high and in breach of safety limits, but ìall diesels are illegalî sounds like a bit excessive. What do you make of it all?

Danny, Edgware

Yes, I’ve read such words Danny, and they are a bit disturbing, and emotive, and frankly incorrect. A diesel can only be truly illegal when it is tested in relation to current and active regulatory limits, by bodies authorised to undertake such testing, which as far as I can see is not the case. The following is a statement issued by the UK Department for Transport that covers the issue.

ìTests have been carried out on a total of 56 different vehicle types in Germany and 37 different vehicle types in the UK, over a period of six months. The Vehicle Certification Agency, on behalf of the Department for Transport, tested a representative selection of the UKís top selling diesel vehicles. The findings provide a snapshot of exhaust emissions from those diesel models when tested in the laboratory, on a test track and during typical road use. Existing laboratory tests designed to ensure emission limits are met have been shown to be inadequate and this is why the UK has secured a tough new Europe-wide real driving emissions test. From next year, vehicles will have to meet emissions limits in real driving conditions across a wide range of typical operating temperatures. This will improve consumer confidence in manufacturers. The UK will be working to ensure that the new rules for real driving emissions and type approval are robust, deliver the expected outcomes, and that manufacturers behave consistently.î

Now in parallel with this real world on-road testing, a new laboratory test called the WLTP, or World Light Vehicle Test Procedure, is scheduled to be introduced in 2017, which should address some of the inconsistencies between laboratory and real world conditions, but the full details have yet to be finalised. To accuse existing diesel vehicles of being illegal at this moment in time is very much factually incorrect, and nothing can be illegal before the law concerned has been brought into effect.

Putting it into perspective, we might argue that any car, diesel or petrol, is illegal when it is travelling in excess of the prevailing national speed limit, but that does not mean that the car itself is illegal, or that any car capable of exceeding such speed limits is illegal. If these real driving emissions preliminary tests establish a situation where thousands of cars become immediately illegal when the new regulations come into force, it is utterly inconceivable that such cars would be banned from the road. Do they suggest that if, for example, ten Volkswagen Golfs with a specific size and power output TDI engine are found to exceed the proposed limits, does that mean that all such Volkswagen Golf variants would be taken off the road? Sensible compromises will be necessary and we can only presume that therefore some modifications to the proposed regulations will need to be carried out.

There are other issues that don’t seem to be being addressed. If a car is tested in an area where the ambient nitrogen oxide levels are already high, or in excess of EC health limits, then it’s pretty much impossible to expect any car to draw such contaminated air into its engine and then emit exhaust gases that are below the proposed new limits. How will the authorities deal with such a situation? There’s a lot more to this situation than meets the eye, and manufacturers are working their socks off to find solutions. To introduce new regulatory limits that will cause utter turmoil does nothing to solve the problems, and we must hope that sensible people will find solutions before these new tests and limits are enforced.

I hope this gives you some consolation Danny, and I’m sure that we will be hearing a lot more about what is actually going to happen before these new limits, or amended ones, are enforced. In conclusion though, and readers should take note of this, it has been established that in many urban situations the highest concentration of nitrogen oxides is inside the car cabin itself. So car drivers are arguably at a higher risk than pedestrians and, that being the case, we need a solution as much as anyone else. But is it our exhaust that’s poisoning the air, or is it the old smoky taxis, the older diesel buses, and the stop-start HGVs like waste collection vehicles. Somebody needs to find out for sure, before they make any silly knee-jerk decisions! Regards,

Doc D

4 Responses

  1. I have recently toiled over buying a diesel or petrol A3, and gone for the former, given its efficency (a diesel ultimately still uses less fossil fuel than a petrol), and the fact that our other cars are diesel (yes, I have put petrol in a diesel before…).

    The backlash against diesels seems to be a little decerebrate. I am all for banning high NO2-emitting diesels from city centres with already high NO2 levels, but surely a Euro 6 diesel that does 70 mpg is fine in the city, especially compared to an old smoky taxi?

    Will those at the top make sensible decisions based on scientific fact? I note an MP at PMQs today was urging Mrs May to get rid of her government diesel cars, and she simply said she is going for petrol-hybrids – which makes sense for city dwellers, who frankly should be on public transport or their bikes anyway.

    Justin Huntingdon
    Norwich, UK

  2. You need to study the post-dieselgate Govt mandated emission tests carried out on a wide cross section of Euro 6 diesels, those tests showed the typical Euro 6 diesel car to be non-compliant by a factor of 6 ftimes the upper limit for Nox, petrol cars passed their more stringent Nox test easily. In simple terms , a single Euro 6 diesel car produces the toxic Nox emissions equivalent of 10 petrol cars

  3. “I have recently toiled over buying a diesel or petrol A3, and gone for the former, given its efficiency (a diesel ultimately still uses less fossil fuel than a petrol),”

    I wish to challenge your statement (above), you need to be aware of the relative yields of diesel and petrol fuel when refined from fossil crude oil.

    Petrol yield is typically 40% by volume, diesel yield is typically 20% by volume, and diesel yield is declining year on year due to the higher need to refine diesel fuel to be compliant with modern diesel cars, requirements such as ultra low sulphur diesel fuel. In simple terms fossil fuel crude needs for diesel are double that of petrol, a 50 mpg diesel has the fossil fuel crude appetite of a 25 mpg petrol car

  4. There is a lot of hot air here as we must all know that its prior to EU4 diesels that are the polluters most of which are local authority contracted vehicles in our area .
    Just ban all the old petrol and diesels prior to the EU4 , this will take a considerable amount of whole vehicles off the roads !Mine are always dealer serviced where they have the equipment to do it thoroughly to spec . Public transport is a disgrace in this country and should be addressed immediately .Its a fact of life if you cant afford a compliant vehicle you should not have one on the road . Why do manufacturers continue to make excessive big engines in road cars 2 litres is enough !Get the suppliers to make better fuel and oils , ban the lesser ones from use . Make learners take a mechanical knowledge test so they know what they are buying . Diesel is best for me living and working rurally .

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