/ Motoring

Would you still buy a diesel?

Amid headlines of manufacturers cheating emission tests and the harmful effects of NOx on our health, is there any room left for a defence of diesel?

Diesels are distinctly out of fashion. With consumer confidence in them shot after various emissions scandals, higher UK road taxes, new MOT rules and some cities around the world banning them outright, driving a diesel seems to be becoming taboo.

Add to this growing public awareness of the effects of NOx emissions and the subsequent plummeting sales, and it seems it may be curtains for diesels.

Decline and fall

Since VW’s ‘Dieselgate’ rocked the world in 2015, sales of diesel cars have plummeted in the UK, falling from 50.1% of overall new car sales in 2014 to just 31.9% as of July, according to data published by the SMMT (Society of Motoring Manufacturers and Traders).

And it’s not without reason. Public awareness about NOx (oxides of nitrogen) emissions from diesels – linked to tens of thousands of premature deaths around the world – has grown massively.

Air pollution from vehicle emissions is a very real problem. In 2017, for example, it took just five days for Brixton Road in London to break its NO2 (nitrogen dioxide) limit for the entire year.

And the results from our new research paints a fairly dirty picture for diesel: on average, the 61 diesel cars we tested produced 0.27g/km of NOx – nearly three and a half times the official Euro 6 limit (0.08g/km).

Diesel defence

But does it have to be this way? Diesels generally produce less carbon dioxide (CO2) and carbon monoxide (CO) than equivalent petrol cars.

And they don’t inherently have to be NOx-spewing monsters. Some manufacturers are starting to produce some squeaky clean diesel cars.

Currently they are the exception rather than the rule, but we’ve found two Mercedes and one BMW diesel car that produce less or the same NOx emissions as your average petrol.

AdBlue & SCR make a difference

More and more diesel cars are using Selective Catalytic Reduction (SCR). It’s an active emissions system that injects urea, most commonly AdBlue, into the exhaust system to cancel out harmful emissions.

And it makes difference. We found that diesel cars with an SCR system, on average, produced about a third of the NOx than cars without one.

So fitting these systems on all diesels could make a huge difference to NOx emissions.

But it’s really a question of whether manufacturers think it’s worth the cost to add these sophisticated systems to their entire range of diesel cars – something that will no doubt be influenced by the tough new on-road emission tests that will be in force for all new cars by September 2019, known as RDE step 1, and will require better real-life emission control than before.

Room for reform?

Some manufacturers clearly do think there’s public appetite for cleaner diesels, a Mercedes spokesperson telling us previously:

‘Our new engines are both highly efficient and produce low levels of NOx. It’s a fact that it’s worth improving the modern diesel instead of banning it.’

That’s one opinion, but it is true that relatively ‘clean’ diesel cars are possible – and available, if you’re willing to pay for them.

The problem is these ‘clean’ examples really are the exception and, it seems, time may already have been called on diesel generally.

But what do you think? Do you agree that diesel has a future if it can be improved? Is the public snubbing of diesel going too far?

What about if someone presented you with a clean diesel car – it produces less NOx, CO2 and CO, and costs the same as an equivalent petrol car – would you buy it or not?


When I replace my diesel car in three or four years I expect that I will buy a hybrid. With the growing popularity, I expect we will see improvements over the models currently on sale.

While great advances in the design of cars have taken place during the time I have been driving, European car manufacturers have received considerable criticism over emissions.

Not so long ago, petrol engined cars were considered dirty. They emitted lead and carcinogenic chemicals. The industry was forced to produce vehicles that would run on unleaded petrol (which could have been done many years earlier) and the introduction of 3-way catalytic converters removed most of the harmful materials from their exhausts. Putting similar effort into diesel engines is bringing a reduction in nitrogen oxides and particulates. Maybe we will see a considerable reduction in the number of new diesel cars being registered but I do not foresee diesel HGVs being phased out in the near future.

I do believe that it would be worth checking diesel engines for emission of nitrogen oxides and small particulates during the MOT test.

All the cars shown above meet the official emission limits. However, when faced with our own tests, which we believe are more realistic and reflect the way people actually drive, the Subaru Forester produces 2.02g/km of NOx – that is nearly 25 times the official limit. The average diesel emission rate among the 61 cars we’ve tested so far is 0.27 g/km of NOx, which is still nearly three and a half times the official limit.

Read more: https://www.which.co.uk/news/2018/08/which-tests-reveal-the-most-polluting-cars-and-the-most-economical-cars/ – Which?

“And the general picture from our new research paints a fairly dirty picture for diesel: on average, the 46 diesel cars we tested produced 0.31g/km of NOx – nearly four times the official Euro 6 limit (0.08g/km).

@aporter (or @elena), would you clarify quickly exactly what you are alleging here. Are you saying that these 46 diesel cars were tested exactly to the EU NEDC laboratory test regime and did not meet the emissions limits required by that NEDC test?

What Which? are demonstrating is that under Which? test conditions, diesel cars generally produce significantly more than allowed by the current lab tests. It is one of the reasons we need the RDE tests.

Hi Malcolm,

W? actually tested more diesels than we originally reported, and the average NOx emission is subsequently slightly different. The convo has been updated.

Let me find out from Adrian how the tests were conducted.

The list of diesels tested here and previously reported in the magazine is not a very long one.

wavechange, I am aware that Which? test differently and we know that cars “on the road” perform differently than under NEDC test conditions – the only test currently where emissions are measured officially. There is now an official EU Real Driving Emissions (RDE) test in operation which will lead to better data and appropriate regulations.

That was not the point I was making. I was asking Which? whether they use the NEDC official test when they say “46 diesel cars we tested produced 0.31g/km of NOx – nearly four times the official Euro 6 limit (0.08g/km).”. The only regulation for car emissions is that stated under the EU’s NEDC test. The Which? statement implies that 46 cars do not meet the official (EU) regulations and that is a serious allegation. I want to clear up exactly what Which? are alleging.

Which? has made no claim that the cars are not meeting the emission requirement under standard test conditions.

The Which? tests are there to help us better understand what is happening under real life.

Thanks Adrian. We don’t see you much on Which? Convo these days, so I hope you will continue to keep an eye on this one.

Hi Malcolm, see Adrian’s response below in answer to this. Thanks, Oscar.

@aporter (or @elena), The question I asked was this:
Would you clarify quickly exactly what you are alleging here. Are you saying that these 46 diesel cars were tested exactly to the EU NEDC laboratory test regime and did not meet the emissions limits required by that NEDC test?

Could you give a direct answer to this please?

I’d also be interested in the precise details of the test used by the contracted external labs which are, apparently, superior to the standardised tests.

That would be very interesting, especially if we can see how the tests compare to the new European tests. I have seen brief details in the past and recall that one of the tests was carried out on a cold engine rather than one at full working temperature, as used in the current NEDC tests.

I’d suggest all tests are superior to the long-outdated NEDC test. The WLTP test, now introduced, was devised to give much more realistic results from today’s cars under more typical European driving conditions. As far as I know, Which? use a similar test regime. I hope in future, if it is not already, it will be identical otherwise their results will not be comparable.

The purpose of the EU tests still remains one to give comparability between vehicles, not “true” figures that everyone will achieve. Given the variety of topography, loads, driving styles, roads types, areas, journey lengths…..that individuals encounter and use that is impossible.

Anyone who has ever driven a car will know that the these factors affect the mpg, but obviously we need to test under standard conditions to compare the fuel economy and emissions of different vehicles.

Even when we have the WLTP and RDE tests are established there may still be a need for Which? testing if this better reflects the way in which we drive.

The whole point of a standardised test is to produce data on the same basis to allow proper comparisons to be made. The WLTP test was developed internationally for a specific purpose. I doubt a third party is going to do better but, in any case, the results could then not be sensibly compared.

What matters to most motorists is what their likely on-the-road mpg is likely to be. It is said that the WLTP should give much more useful results than the NEDC, although it is not its primary purpose. The best way to get an idea currently is to go to something like Honest John mpg, where thousands of motorists give their own mpgs and they are averaged for each brand and model. Which? might be better doing something similar – Which?mpg.

@aporter, so do Which?’s tests follow the WLTP exactly?

The WLTP will be the only test the EU will allow for “official performance results” that can be published as far as I know, and therefore the one manufacturers must follow.

Unless manufacturers adopt our test procedure, our tests will not be identical.“. Presumably what you mean is your “results” will not be identical. We must be careful not to confuse the purpose of the EU WLTP and RDE tests. It is to get comparable results between vehicles, to be as realistic as is possible under standardised conditions, and to form a common basis upon which regulations can be based. That is not necessarily the same as yielding everyday performance (which will vary on driving style etc). So you cannot use a different test regime (Which?’s) to criticise the results from the WLTP.
I’d like to be clear about what Which? are actually using their figures for.

This piece ignores another major source of emissions from diesel engines, those in commercial vehicles. I’d suggest the likelihood of all these becoming hybrids or electric in the near future is remote and therefore work will be concentrated on ways to make them cleaner, as has been happening for many years. We are willing to pay a premium for a hybrid, so why should we not do so for a clean diesel? Clean diesels might currently be the “exception” but they show it can be done, so the exception could become the norm.

And they don’t inherently have to be NOx-spewing monsters. Some manufacturers are starting to produce some squeaky clean diesel cars.

Would I buy a clean diesel? Probably, or a diesel hybrid if I drove into town a lot. It is more efficient than petrol, and I assume would remain so when integrated with an electrical system. Use it for economy on the open road and the electric in town for zero emissions.

Incidentally, if you have a robust case, then language like “spewing monsters”, confidence “shot”, devalue its impartiality but no doubt some feel will make a better headline. I would much prefer Which? to offer balanced appraisals and reports rather than indulge in emotive language.

Modern diesel engines are fitted with particulate filters. In order for them to regenerate (burn off accumulated carbon) they must periodically be run under load for a period to reach the required temperature, otherwise the filter can become irretrievably blocked and must be replaced at considerable cost. I wonder how practical diesel-electric hybrids would be, since the engine is less likely to be run under the required conditions for regeneration than in a diesel powered vehicle.

Presumably a burn-off cycle could be produced that ensured at appropriate times the dpf was properly cleaned.

Regeneration of a pdf requires a diesel engine to run under load for sufficiently long to allow the cleaning process to take place. I suspect it would be necessary to prevent the vehicle from using battery power until the process to continue. It seems simpler to make use of a cheaper petrol engine and the idea of a hybrid is that it is run on battery power where possible. The small number of diesel hybrids suggests that they might not be the best option.

I agree Wave. Diesels are better for long haul (lorries and cars); electric is better at short hop (cars, milk floats etc) petrol hybrids bridge the gap.

It does not require so long these days for the diesel engine to deal with the dpf, so I don’t see that as a problem. However, for those who use their cars for any distance and don’t want to keep recharging the batteries, running routinely on diesel out of town seems a good option, where the economy of diesel is used,

With a PHEV the bulk of them seem to have a low electric range. https://www.autotrader.ca/newsfeatures/20180710/2018-phev-and-ev-range-and-charging-times/
For many out of town journeys you’d need to use the normal engine so for a journey of any reasonable length a diesel might be more economical than an Atkinson cycle petrol?

I don’t know whether it is for technical reasons or personal choice, but at present the preferred option is petrol-electric hybrids. I would prefer that we start thinking about ways of cutting down the amount of traffic on the roads and creating less pollution.

See https://conversation.which.co.uk/travel-leisure/rail-trains-prices-soar/#comment-1541495 for possible solutions. 🙂 I think Elena has heard what I have said 🙂 🙂

There appears to be scope for improving the efficiency of diesel engines, and reducing NOx emissions, by using over-expanded cycles such as the Atkinson or Miller. I expect, under pressure from regulations, that we are going to see more development of conventional engines, particularly diesels.

As far as reducing CO₂ emissions and global warming is concerned, we hear little about the impact made by aircraft and shipping. A typical aircraft seems to produce around the same CO₂ per passenger km as a car. So maybe cutting holiday trips abroad would be beneficial in saving the planet. Too gruesome to contemplate, like most actions that impact on us as individuals.

For some time I have been pointing out that petrol engines used to be very dirty, emitting lead and carcinogenic chemicals in their exhausts, and that if the same amount of work was put into developing diesel engines they could be much cleaner. That’s for the future and as Which? rightly points out, cars that emit far more nitrogen oxides than apparent from current (NEDC) testing reveals.

The health risks of nitrogen oxides for everyone, particularly those with asthma and COPD, are well established but there has been less focus on small particulates (often named PM 2.5) that are not seen as visible smoke.

Current diesel engines used on cars make use of diesel particulate filters that can be troublesome and have a limited life, and equally troublesome EGR valves that allow soot to enter the inlet manifold, contaminating the oil and the inside of the engine. I would not be surprised if we see the development of high temperature catalytic converters to address these problems.

It would be good if Which? raised awareness of the environmental impact of air travel. My approach was to stay for a holiday in places that I was visiting to attend conferences or meetings, avoiding travel costs. Obviously there are environmental benefits.

If I was buying a new car today it would be a petrol hybrid. Not so long ago I did not think that electric vehicles had much place other than for city cars, but we have moved on.

Developing cleaner diesels is clearly for the present, as the examples from MB and BMW highlighted by Which? show. The link provided by Moi-meme shows what Bosch have to say about the potential for cleaner diesels. Clearly a lot of work has gone on in the past to arrive at Euro 6, and is still going on to produce even cleaner power plants.

What seems often overlooked is the diesel goods vehicle contribution. Their engines will need to be cleaner in future to reduce pollution. I’d suggest therefore that with the focus on pollution, there will be even more work focused on developing reduction solutions.

As far as Which? ” rightly points out, cars that emit far more nitrogen oxides than apparent from current (NEDC) testing reveals” this is hardly revealing news. It relates to the difference between performance on the road, and performance in the laboratory under quite different test conditions, as NEDC is so out of date. So it really adds nothing to the debate except to stir up concerns in a misleading way, particularly no doubt with the undiscerning press.

With the WLTP we will have much more realistic test results. The RDE pollution testing now being used will give much more useful information about what happens on the road under real life conditions and both help set regulatory levels and help developments in pollution reduction.

MikeL says:
17 August 2018

NOx and particulate pollution create local problems and have technical solutions. It’s CO2 emissions that really matter: climate change threatens the whole planet, and the only way to prevent it is to take every possible measure to emit less. Well-designed diesels are clearly the better option for most road vehicles until battery technology improves significantly in charge density, life and sustainability. I’d buy a (good) diesel every time but for the misguided political hostility that threatens diesel drivers at every turn; as it is, my next car will be petrol.

One way of cutting carbon dioxide emissions is to cut down on driving, overheating our homes, etc. That’s something we can all contribute to.

I would be interested to know how much carbon dioxide is produced by cars compared with that produced by humans and other animals.

It’s often said that if we plant more trees, they will help remove carbon dioxide. That’s true, but other plants do the same. Covering gardens with block paving etc. is not a good idea.

Not so sure I agree, MikeL. Nature is a wonderful leveller of things slightly out of balance. CO2 is present in the air to a small but measureable amount wherever there is life. If CO2 goes up by even the tiniest amount in a given acreage, the plant life grows more vigorously to take advantage of this and the chlorophyll process cracks it back to C (which the plant “eats”) and O2 which it releases back into the air.

I just came across this in passing (as you do). It may be that planting particular species in our towns and cities could help reduce both CO₂ and NOx. I haven’t calculated how much planting would be needed to be effective.

Roger – I have long assumed that nature is capable of buffering changes in carbon dioxide level in the atmosphere but our oceans – which make a major contribution – are becoming more acidic and recorded levels seem to be getting out of control: https://climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/

What’s most difficult to assess is obviously the impact of human activities.

Yes – acidity is worrying. I wonder if acid-loving (and pH-upping) marine life will step up to the plate by being more prolific, and correspondingly base-loving (and pH-downing) life will slow down or even hibernate for a few decades?

That’s an interesting thought, Roger, but I understand that much of the carbon dioxide removal in the oceans is by chemical processes that are affected by pH. I stand to be corrected.

It would seem that our car buying has been swayed, in the past, by politicians and environmental experts. So petrol became less popular because diesel ceased to be the noisy, smelly and under-powered engine that it had traditionally been and became a sophisticated unit that pulled well, didn’t vibrate too much and gave fantastic MPG. Petrol was the greater pollutant. Now, of course the reverse is almost true. Petrol is no saint but the lesser of two evils and its combination with battery power has helped too. The fact that many of us bought diesel because it had improved so much means that quite a few are on the road today. My first diesel in 2006 left a trail behind it when accelerating sharply. The next ones didn’t. The exhausts look clean with no trace of carbon deposit at their ends. However, according to tests, they do pollute more than they should and the various experts have highlighted this. The obvious result is that no one wants to buy a diesel car any more. That’s fine if the car you have to trade in is not worth much, but if it “did” have some value before public opinion changed, the incentive to change it now is less attractive. I must accept that I have lost several thousand pounds, just like that, and I now have to recoup that value by using the vehicle instead of upgrading it any time soon. I happen to be very happy with it in all other respects, so this is no hardship, but I’m not helping the planet in my selfish desire to save money.

Moi-meme says:
17 August 2018

Gasoline (petrol) produces finer and more pernicious particulates, hence the development of GPFs, gasoline particulate filters.

Here’s how I buy my cars:
1) I find my current car is no longer economical to MOT/repair
2) I have £x & need to consider road tax, insurance group & MPG.
3) I usually go to a car auction knowing that 4-5 cars fit the bill.
4) I bid & hopefully drive away with another car I can drive into the ground circa 200k miles.
5) choice of car is very dependent on what’s available & ‘common’ so parts & repairs are economical.
6) I have owned diesel cars for 30+ yrs. I do very little town driving. Last car cost £7k VW Passat estate. Bluemotion 1.6 TDI which has since been recalled & refitted.

This introduction states “And the general picture from our new research paints a fairly dirty picture for diesel: on average, the 46 diesel cars we tested produced 0.31g/km of NOx – nearly four times the official Euro 6 limit (0.08g/km).”

I believe some people will infer from this statement, and the one in the associated article, that these 46 cars do not meet EU requirements. That is untrue. Adrian Porter has clarified this above. The cars all meet the laboratory test requirements of the EU test (NEDC) that approves them for sale.That test has an emissions limit that they all meet.

When you then drive a car on the road under more realistic conditions (and the NEDC falls very short in this respect) the emissions are higher than in the lab. That does not mean very much; you can use a figure from a laboratory test and relate it to what happens on the road, and set a regulatory limit on that basis. It may well be what the NEDC test designers did.

There are, currently, no on-the-road limits (regulations) against which car emissions can be judged, therefore this “46 diesel cars we tested produced 0.31g/km of NOx – nearly four times the official Euro 6 limit (0.08g/km” is meaningless as the Which? tests do not relate to the test for EU limits.

We now have the introduction of the WLTP test (driving cycles much more representative of current European driving and vehicle technology) and an on-the-road standard emissions rest that will yield much better data on which to base regulatory limits.

Which?, I suggest, needs to be more careful about how it presents and comments on its own data to avoid it being misleading or liable to misinterpretation. I want rigorous testing used and presented in an impartial way.

However, with the recent and predicted higher atmospheric temperatures, should not CO2 emissions be back in the picture too?

That will presumably include the CO₂ emissions from power stations that use natural gas to produce 40% of the electricity used to charge EVs. Using natural gas in this way is less efficient at providing energy for a car than direct combustion in the a diesel car.

Moi-meme says:
17 August 2018

It seems Diesel engine technology is still advancing toward ever-cleaner diesels, as component companies develop increased reduction in NOx emissions.


Perhaps the article should also consider the diesels from BMW and Mercedes that may have a defeat cycle for the Adblue …… or probably not.

and actually cheating lorries

Adblue with Peugeots apparently is every 12500 miles and is part of the servicing but it is 8000 with a VW Passat which then leads to a question as to whether different speed profiles will give different mileages! Passat has a 13litre tank which at 1.5l per 620 miles …..

Unfortunately one can foresee that s ome of the public will be happy to cheat when they have a diesel car to save money. Confiscation now doubt would be a effective deterrent. : )

The problem with these convos is the “may haves” that are used to further a particular stance. I’d like to see facts and substantiated information, not conjecture. I have no axe to grind either way, I just want straightforward honest reporting. Which? has a duty to do this for its members.

Thanks for the link Moi-meme. Here is an extract:
But even today, vehicles equipped with the company’s diesel technology can achieve as little as 13 milligrams of NOx in standard legally-compliant RDE cycles. That is approximately one tenth of the limit that will apply after 2020. And even when driving in particularly challenging urban conditions, where test parameters are well in excess of legal requirements, the average emissions of the Bosch test vehicles are as low as 40 mg/km.

A combination of advanced fuel-injection technology, a newly developed air management system, and intelligent temperature management has made such low readings possible. NOx emissions can now remain below the legally permitted level in all driving situations, irrespective of whether the vehicle is driven dynamically or slowly, in freezing conditions or in summer temperatures, on the freeway or in congested city traffic.

Even with this technology, the diesel engine has not yet reached its full development potential. Bosch now aims to use artificial intelligence to build on these latest advances. “We firmly believe that the diesel engine will continue to play an important role in the options for future mobility. Until electromobility breaks through to the mass market, we will still need these highly efficient combustion engines,” commented Denner.“.

So looks like a good future for diesels. I wonder why Which? do not find this sort of information to include in their reports. Are they not aware of what is going on?

Equally, Which? could look at possible developments in electric vehicles in the same timescale, but at present it is focusing on cars that are currently on sale. If we are going to look to technical developments then perhaps use some independent source of information rather than information from companies, which can be a tad optimistic at times.

I expect those companies expert in the field have the knowledge to advise us on developments.

The trouble is experts in companies are not independent – qv Judge John Deed and the phone masts…

I agree that it is difficult to provide impartial data when one is governed by commercial interests.

Such interests can include promoting sales for all sorts of commodities, including actual products and subscriptions for newspapers, magazines and learned societies.

We perhaps need to decide what the expert is doing.

If it is about commenting on, or reviewing, a current technology, say, then an expert in a commercial organisation will probably concentrate on his organisation’s work which he/she knows intimately . However when I worked in industry and attended conferences, gave lectures, attended technical committees, we were not so insular that we did not discuss and give credit for developments throughout our industry. It generally worked in everyone’s favour.

If we are using an expert to get results within their organisation, such as developing better pollution controls for an engine, then independence is not an issue, but independent thinking is.

Another problem that crops up, particularly in the media, is when “experts” are invited to comment on matters that lie outside their actual expertise.

Hi Malcolm. Do hope you’re well. I agree, and straightforward, honest reporting has been a staple of Which? for a very long time. As with many convos, this one was born from one of our recent investigations. The news story can be read here:


Our news stories often tend to contain the meat of the investigation, while supporting convos can help generate debate around the subject and cosnumer experiences – but we do try not to duplicate the news stories over here where we can.

Also, Oscar has rounded up all your outstanding queries here and he’s presented them directly to Adrian for responses. When I started in the team I stated that I wanted to see our authors replying to our community as much as possible – I’m determined to make that happen effectively.

@gmartin. Hello George, hope the house move went well.

The news story includes, for example “All the cars shown above meet the official emission limits. However, when faced with our own tests, which we believe are more realistic and reflect the way people actually drive, the Subaru Forester produces 2.02g/km of NOx – that is nearly 25 times the official limit. The average diesel emission rate among the 61 cars we’ve tested so far is 0.27g/km of NOx, which is still nearly three-and-a-half times the official limit.“.

You cannot compare the results from the WLTP tests, or Which?’s variant, with the NEDC test results. The tests are not the same. Relating what happens in a laboratory test to will will happen on the road under actual driving conditions is difficult when the lab test is so unrepresentative of real life. Hopefully WLTP and RDE will change that.

I am keen to see pollution reduced and properly regulated to help that. However the way Which? has portrayed this is quite misleading. It needs to be careful to separate its apparently preconceived ideas of a cheating car industry from the facts, and present those in a professional and informative way. Their attitude is rather clearly made apparent when they publish headlines like this:
Nearly 80% of diesel cars exceed emissions limit in latest Which? tests
17 August 2018

I hope the response from Which? will be to be more careful to present information in a way that does not mislead; as you say, honest and straightforward.

Which? say “ The cars do not meet Euro 6 in Which? tests, “. This again is a quite misleading statement as the Euro 6 requirements are only valid when assessed under the NEDC test regime imposed by the EU. A different test regime will produce different results, where Euro 6 has no meaning as far as I am aware.

Which?, unless i have this all wrong, need to be much more careful about what they say and publish.

@aporter, now we have a very misleading press release:
Nearly 80% of diesel cars exceed emissions limit in latest Which? tests
17 August 2018
Most modern diesel cars are much dirtier than official limits, according to ongoing Which? tests that show that the majority exceed official emissions limits when put through more rigorous real-world tests.

This is nonsense, as far as I can see. There are, as yet, no regulatory (official) limits that apply to on the road performance. The only tests are the NEDC laboratory tests against which emissions are assessed and cars sold meet these. You cannot criticise a car against a limit that does not exist.

It is quite wrong, in my view, for Which? to issue such incorrect information to the press and, unless you can support the claim that these cars do not meet the regulatory (EU NEDC) limits then you should issue a correction.

The press release concludes:
Alex Neill, Which? Managing Director of Home Products and Services, said:

“The current official tests fail to measure the actual level of emissions that cars are producing on our roads…..
Most diesels we assess are producing far more NOx in our tests than official limits allow. The new official tests* should help reduce harmful emissions – but we will continue to penalise any car we find that produces excessive levels of pollutants in our tests.”

First, there is now an official test being introduced to measure the “!actual level…….on our roads”. The Real Driving Emissions test. Why do you not say this?
Second, most diesels do not produce more NOx than “official limits” allow. There are no “official limits” that can be related to your tests, as above.

Unless I have totally misread or misunderstood what you are saying, I see this as misrepresentation of the situation and quite deliberately misleading.

Press releases, as such, are caught between two stools: on the one hand they need to convey information in such a way as to encourage journos to write about it. On the other hand there are probably more fingers than journalists with engineering degrees in the entire country. If Which? wants to stimulate debate about diesels, pollution and test standards then it has to produce press releases which are short (very, very important), attention grabbing (essential) and clearly a matter of public concern.

It’s then the journalist’s responsibility to make further enquiries from Which? to establish the veracity of the release and any further details.

It’s not that I’m inherently defending Which? in this instance, but I can see the problems for what they really are and sometimes the only way to keep the profile of a specific debate in the public consciousness is to issue press releases along those lines. We’re already bombarded by headlines on health-associated matters, penned by journalists who quote statistics but who have little to no training in statistics, probability or percentages to help them comprehend why a 50% increase on a miniscule base figure isn’t a big deal.

You’re making some very serious allegations, there, Malcolm, and I’m simply trying to explain the difference between a press release and a paper on the subject in question.

Absolutely no doubt that the Which? article is misleadingly crafted. All it takes is a simple sentence or two to explain that the cars are in accordance when tested but the test parameters are artificial and in real world use the limits are routinely breached.

If Which? was truly a consumer body employing scientists rather than wordsmiths perhaps it would discuss how EU regulations are tweaked and twisted and not necessarily the best for consumers. One might recall the lack of coverage of the EU regulation where vacuum cleaners suction was measured when empty rather than perhaps the more likely and common half-full.

That the EU measuring regulations were changed after nearly a decade of Dyson forcing the issue illustrates that often businesses are writing the rules. And that change, even if highly logical given a change in technologies, is not something that the bureaucrats/industry will want to change even if it is beneficial for consumers.

A similar case with the EU and the washing machine manufacturers where the 60C dial on the washing machines are in no way linked to what the consumers might think is the wash temperature. Given NHS requirements of it’s staff who are very often required to launder uniforms at home and to wash at above 60C this , at least in the UK, has health implications.

It would have been quite simple to mark dials as =60C and have an a genuine 60C wash also. Who fought for this clear distinction? Apparently no one as all that was considered was using less energy as the only criteria; and lying to the public seemed simple.

Perhaps Which? needs to be more interested and explanatory about EU regulations and criticise defects at the time of discussion and introduction. Embarking on campaigns years after may be good but does highlight that Which? is missing tricks.

Six years after the national Firemans body calls for metal backed home appliances Which? joins in. Seems if it used its muscle earlier in time and refused to recommend any plastic-backed appliances then and supported the Firemans call then perhaps some major fires would have been avoided. Or at least an more educated public would have been aware of the problematic nature of plastic back panels.

I think the press no longer has the people to question what “sources” tell them. That is why it is important that a body that is presumed to be independent and impartial such as Which? gives out information that is correct.

My comment above points out where I believe the comments made by Adrian and Alex are defective.

Patrick Taylor says: Today 09:15

Absolutely no doubt that the Which? article is misleadingly crafted. All it takes is a simple sentence or two to explain that the cars are in accordance when tested but the test parameters are artificial and in real world use the limits are routinely breached.

Patrick: but doesn’t the sentence “Most modern diesel cars are much dirtier than official limits, according to ongoing Which? tests that show that the majority exceed official emissions limits when put through more rigorous real-world tests.” say that? Granted not as precisely, but from that sentence I read that most modern diesel cars exceed the emissions limits when driven under different circumstances to the test.

Granted, it’s headline grabbing – sure, but I imagine Which? has the findings which prove what it’s claiming.

malcolm r says: Today 09:18

I think the press no longer has the people to question what “sources” tell them

I’m not sure the press ever did, when the subject is technical or scientific in nature. Look at Kate’s mobile ‘phone debate. Kate has interviewed a very respected specialist in the subject but her word count limitation means she has to leave a lot of the detail out and summarise the important parts.

That then attracts anyone with an interest in a topic to consult wiki on the matter and contest Kate’s findings. And we all know that wiki is hardly the most reliable source as it’s open to anyone to edit.

This is where you need experts. For me, anyway, an ‘expert’ is someone whose studies of a specific and well defined area have been recognised by the academic community through the award of an advanced degree – PhD being the most frequent, with DSc and DLitt recognising a continuing interest in and study of a particular field.

Kate was the go-between in her topic, attempting to make sense of what is at once both a highly specialised medical field and a subject of common concern and explain the issues (which I thought she did very effectively and cogently) to a lay audience.

It’s difficult. The subject specialist has a specialist vocabulary, which many won’t comprehend, and the expert is innately familiar with procedures and terms others may not know. But in the age of the internet, all too often we come to believe we all know the answers, since we can look them up.

There’s an argument that goes if you can look them up and understand them easily then they’re probably wrong. There are (I think) three of us in the regulars whose fields of study and experience are such that we could probably bore for England, such are the specialisms, and this is the dilemma any Which? writer faces: how to get the message across without drowning it in a sea of detail.

It’s a tough job and while I agree that Which?’s remit is to communicate effectively on the pertinent aspects of any campaign I also recognise the essential problems in so doing.

an ‘expert’ is someone whose studies of a specific and well defined area have been recognised by the academic community through the award of an advanced degree – PhD being the most frequent” A very narrow view of an expert. Someone who has progressed from a first degree to a PhD will be working in a very narrow topic and hardly have amassed enough experience and knowledge to become an expert.

Very many people in industry, for example, work in very specialised areas with teams of like people, and accumulate a great knowledge in that field through both study and hands-on application. These are experts who have made things happen. Many of our great engineers may not have been great academics but made things work. Real experts have not just been through a learning process but have “done it”.

My definition of a specialist is someone who knows more and more about less and less until eventually s/he knows everything about nothing.

I agree with malcolm that Ian’s definition of “expert” is unduly narrow for many cases.

For example, only academic studies are likely to result in the awarding of advanced degrees.

A quick Google says an expert is “a person who is very knowledgeable about or skillful in a particular area”, which seems not over bad to me.

I do, however, agree with Ian’s notion that expert status is gained by the recognition of others, as opposed to by self-promotion.

I think there are too many self-appointed internet experts out there, so internet sources (including Wikipedia) must be treated with care. Wikipedia is usually OK for non-controversial data, or for its references to other, quality assured or official, works.

For academic subjects, properly peer reviewed articles can be good published sources, even if you have to buy your own copies of them. But, in field such as engineering, we generally expect key documents and data (how about the design and testing of a motorway viaduct for example?) to be subjected to far greater verification and quality assurance than is typically carried out when peer reviewing a journal paper.

All that said and done, I still prefer an “ex” is a has-been and a “spert” is a drip under pressure.

My old mentor Charlie Martin CBE used to like that definition too. He used to say that, thanks to a wide ranging apprenticeship, he started out knowing “nothing about everything” instead of “everything about nothing”.

malcolm r says: Today 10:07
A very narrow view of an expert. Someone who has progressed from a first degree to a PhD will be working in a very narrow topic and hardly have amassed enough experience and knowledge to become an expert.

Well, you’re right about the narrowness of the topic, something which I also noted. But the Postgrad student also has to possess a very wide ranging knowledge about the field in general. However, I do take your point about experience. The top experts will not only be extremely well qualified but they will have had a great deal of experience working in their field of study, however narrow.

Derek: you’re spot on about peer reviewing. New Scientist noted sometime ago that certain ‘popular’ subjects were attracting so many PhD theses that almost half are now not being peer-reviewed. The top two were Sociology and Psychology.

Car manufacturers are required to publish fuel economy figures (usually expressed as miles per gallon, or ‘mpg’), along with exhaust emissions data (air pollution), each time they launch a new car. These are the figures you tend to see in adverts and brochures.

And up until 1 September 2017, these figures all come from the previous European Commission test protocol, the NEDC (New European Driving Cycle) which has been widely criticised as easy to dupe, open to loopholes and not being challenging for modern cars.

Read more: https://www.which.co.uk/reviews/new-and-used-cars/article/how-we-test/how-we-test-mpg-and-emissions – Which?

My confidence in Which?’s objectivity and ability (or wish) to inform rather than inflame has taken another hit when I read this kind of statement from them. They seem obsessed with trying to discredit the industry.

– The only figures manufacturers can publish for CO₂ and mpg are those derived under a standard test dictated by the EU (NEDC) despite everyone knowing they are very unlikely to be representative of real life driving.
– that NEDC test is out of date, and that is why the result are of poor quality, not because the manufacturers cheat.
– “easy to dupe” is a silly statement. The NEDC test has loopholes, but the reports that analyse the effect of all these loopholes, if they are used, show their effect on the results is relatively insignificant.
– “not being challenging for modern cars”. I’ve no idea what this comment means. Car technology has changed greatly since the last revision of the NEDC test 21 years ago, so it is no longer appropriate as a test regime.

Come on Which? Let’s have impartial and factual reporting.

I agreed with your earlier concerns on this topic, Malcolm, but believe you are stretching several points here in order to enhance your earlier (valid) contentions.

malcolm r says: Today 09:10

My confidence in Which?’s objectivity and ability (or wish) to inform rather than inflame has taken another hit when I read this kind of statement from them. They seem obsessed with trying to discredit the industry.

I thought the industry had done a pretty good job of that itself.

Thanks Roger. I was simply pointing out what, in my view, is a biased stance taken by Which?, examples of statements that show this, and what I see as sensible counters.

This attitude by Which? is not new. A year or two ago in their Car Magazine they stated that many car manufacturers failed to meet emissions regulations on the road, or words to that effect, in a way that strongly suggested they were cheating,. They had overlooked or ignored the fact that there were no regulations for on-the-road emissions. I did contact Which? direct about this in that instance and they admitted that what they had published was not true. However they refused to print a retraction.

…even the Daily Mail sometimes prints retractions. They use words along the general lines of “as a newspaper dedidicated to truth, justice and British fair play, we’re not above admitting we sometimes don’t get our facts right…”

Gosh, I’m just imagining the concept of “impartial journalism” . (Note to self, must add this to my list of favourite oxymorons.)

I do like “dedidicated” :-). Newspapers have their own (often proprietor’s) agenda and frame their reporting accordingly. Even Private Eye has, particularly on Brexit. However, Which? should not have an agenda nor behave like a newspaper.

Sorry about the “dedidicated” (SP). I wasn’t commenting on the Grauniad.

Would I buy a diesel-engined car?
Yes, if it were economically sensible, provided that it delivered low NOx and low PM from the tailpipe.
In my case, the economics don’t add up, because I usually cover less than 5000 miles in a year so I drive a small petrol-engined hatchback.
My son uses a 12-year old diesel Volvo CX90 for full loads on long hauls only (avoiding city driving). His view is that its inherent fuel economy and low expense make it worth keeping, and the low value of the car means he worries less about the car being stolen or damaged. His “local” driving is all petrol-fuelled.

Gordon Housley says:
18 August 2018

Encouraging results for the best diesels but the worst are a real turn off. I wouldn’t buy another diesel anyway because: Firstly there is the major risk from carbon particulates (also rules out petrol) and your report ignores the environmental costs of obtaining fossil fuels.

I could report the issue with manufacturers published data in another way.

“Car manufacturers attract criticism for publishing performance figures – mpg and CO₂ – that do not accord with what happens in reality, and for excessive NOx emissions. However, the performance data that are published are dictated by the EU; they are produced using a standard series of tests in a laboratory that all manufacturers must follow and only the figures produced in those tests are allowed, by the EU, to be published.

This approach is good in principle because it gives a level playing field upon which performance data is produced and thus enabled comparisons to be made between cars, its primary purpose. It was never intended to give real life performance data.

The problem with this is the test, known as the New European Driving Cycle, “NEDC”, was devised long ago and last updated in 1997. It reflects neither the current driving styles in Europe nor modern car technology, both of which have changed substantially over the last 20 years.

Belatedly, perhaps, the EU has therefore introduced a new test procedure for the laboratory that does correct these deficiencies. It is based upon an internationally-agreed test procedure where the driving cycles and conditions are adapted to suit the European experience. The test is called the Worldwide Harmonised Light Vehicle Test Procedure – WLTP – and will give much more realistic data that manufacturers are allowed to publish.

In addition, the NEDC laboratory test for NOx emissions was particularly unrealistic; the results bore little relation to what happened on the road under real driving conditions. This causes great concern because of the high levels of NOx in built up areas and its effects on health. The EU has now developed a test that takes place while driving on the road and measures emissions under real-life conditions; this is the Real Driving Emissions test, or RDE.

These new tests will produce more realistic data on car performance under real-life conditions, both for publication and to enable sensible limits to be placed on emissions. The cars produced by manufacturers will need to meet these new limits for them to be released for sale. Gradually reducing limits will drive the design of better, less-polluting, engines.”

Sadly, probably not, since most manufacturers look at current trends and probably decide that there is no point refining diesel or petrol cars further. All efforts have now to be directed to make their electric locomotion work better than their competitors.

Without the compulsory emissions standards being altered would the manufacturers research cleaner engines – The issue which prevents me from switching from a diesel is the mileage I have to do. Hybrid / electric need to look at the battery life and if the hybrid is really having an impact on the longer mileage. On the matter of environmental with respect to the batteries what impact do they have on the environment when you consider the shipping etc. I am glad that diesel is being cleaned up – perhaps we need to look at the electric option though and some form of better mileage from battery power – with governmental investment. One of the contributors talks about the impact of fossil fuels – and they do impact on the environment – but so do the nickel cadmium batteries.

Those of us who live in the country and visit smaller towns don’t have the facilities of the metroploitan cities where the majority of the decisions are made.
Sorry turned into a rant!!!!

So I think the whole transport issue and the love affair we have with our cars needs reviewing. Out of city transportation and combined transport hubs (train, bus, metro) needs a radical overhaul to get people out of their cars.
So no I won’t give up on diesel as the non fossil fuel alternatives are either too expensive for the range needed or insufficient range and model choice (plus expensive).

While I think many manufacturers, in general, innovate to improve their product and its performance, the use of regulations ensures that all meet a basic standard. Many. as now, will exceed the standard. I agree when the focus shifts to areas of less economic concern to the motorist, such as NOx emissions, this does drive development in that specific area.

We should get people out of their cars wherever sensible in towns and cities. This means a much better public transport system than we have now.

My 2015 2 litre Jaguar XE 180 bhp complies with Euro 6 and is road-taxed at £30. On a recent motorway trip of 350 miles driving at the legal limit it averaged 70 mpg – a figure I have never seen before in any car.
I personally will never buy another German car after Audi fraudulently misrepresented emissions on my last one. Why are you plugging Mercedes and BMW rather than Jaguar?