/ Motoring

What’s the truth behind car emissions claims?

Come clean on fuel claims

Our testing has found that almost all modern diesel cars exceed official emissions limits when tested in real-world conditions. We even found some hybrids breaking the limits too. So how can we trust car emissions claims?

Consumer news in 2015 didn’t get much bigger than the Volkswagen (VW) emissions scandal. The ramifications were (and still are) huge – not just for VW and the owners of affected cars, but for the whole motor industry.

Our testing is different to the official testing procedure used. It still takes place in a lab, but we use more challenging and realistic driving cycles to provide more accurate figures.

So using our lab results on over 300 cars that we’ve tested since 2012, we did a deep dive on the data. And the results were interesting.

It’s not just VW – and not just diesels either

What we found is that it’s not just VW that have been pumping out some peculiar claims. We looked back over three years’ worth of data, across all manufacturers whose cars officially comply with modern emissions regulations, known as Euro 5 or Euro 6 depending on the age of the car.

What we found was an astonishing 95% of diesel cars exceeded oxides of nitrogen (NOx) limits in our testing. The worst offender emitted 15 times more NOx as its Euro 5 engine is permitted to.

And it’s not just diesel engined cars either. We found that one in ten petrol cars produced so much NOx that they too are breaking emission limits. Now, petrol cars do also produce NOx, but this is supposed to be in such small quantities that it’s of little significance and well under the limits set. The worst offender we found emitted 15 times more NOx as its Euro 5 engine is permitted to.

Carbon monoxide

We also found two thirds of petrol cars are creating far more carbon monoxide (CO) in our tests than EU limits.

CO is different to carbon dioxide (CO2) – CO2 is harmful to the environment and your car tax is based on how much CO2 your car creates. CO on the other hand is much more harmful to human health and has no effect on car tax.

Worryingly, in our tests, two thirds of petrol cars put out more CO into the air than they’re allowed to. The worst created more than five times the amount of CO than the official limit. And it’s not just sporty or big cars that are to blame – several superminis with small capacity engines are among the top offenders. And some were so bad that they couldn’t even meet the early ‘Euro 1’ limits from 1993 – which are pretty lenient compared to modern standards.

To our surprise we also found some hybrid cars are also breaking emission laws. Testing revealed that some petrol-hybrid cars emit more CO than they’re allowed – in fact one petrol-hybrid was the 11th highest CO emitter we’ve found so far.

We’ve also identified a diesel-hybrid that produces more NOx than limits allow. And what makes this even worse is that there is no special lower limits that hybrids are held account to.

So what now?

We want you to be able to trust car makers’ fuel emission and efficiency claims. We need a stringent, independently audited test regime in the EU. It’s no coincidence that the VW scandal broke in the US, where such a test regime operates. The flawed European system allows carmakers to declare lab figures that rarely bear any relation to real-life emissions.

As a VW owner I’m currently awaiting the ‘fix’ to my car, as I’m sure thousands of you are. Last week we heard that VW has no plans to compensate VW owners in the UK, as they have in the US. But I’m curious to know whether this fix it will have any bearing on how my car performs, or on the pollution it produces in daily driving. VW has insisted that there will be no change to performance, but I’ll wait and see.

Since September, more than 78,000 people have backed our ‘Come Clean on Fuel Claims’ campaign. If you agree that more needs to be done to make car manufacturers come clean on emissions claims then back our campaign today. Also, tell us what you think about your car in our Car Survey.

So what do you think about these car emissions claims? Have you been affected at all?

*All Euro dates refer to new car registrations


How disappointing you have not published the results of all your tests across makes and models .

It would be interesting to know more. Maybe the next issue of Which? magazine will have more detail.

Fortnum says:
22 January 2016

The Euro NOX limits are not legal limits that must never be exceeded by a vehicle in any circumstances as suggested by the article, but a limit that must not be exceeded under specific conditions which are the same for all vehicles being tested. All vehicles will break the limit at some time or other when the engine is put under load such a climbing a hill, including hybrids when they run out of battery power. The test provides a single common point of comparison for all cars for setting targets to improve combustion efficiency. The statement that vehicles are “spewing out more NOX and CO than limits allow” , or “defying emission limits” is only correct if the vehicles are being driven to the NEDC cycle otherwise it is pure miss-statement to support a flawed arguement.

The current test may not be representative of normal driving conditions, but the same test has to cater for all vehicles and what may be a slow test cycle for a Jaguar may be flat out in a Reliant. The more challenging driving cycle proposed by Which implies a greater work rate and a higher fuel consumption. The NOX limits would have to be adjusted to reflect this change.

Cannot join in the technicalities of this debate but have tried to see if my Roomster Scout 2008 is affected. Did the following:
Skoda website-http://www.skoda.co.uk/owners/dieselinfo/check-your-vehicle/
neither the vpn or reg number worked!
Phoned Skoda customer services who informed me that my car was not affected and that re emissions problem in general it was not the software at fault but emissions were being ‘mis-read’!

Should have added I cannot find a full list for affected Skodas anywhere. Article links I have tried just do not bring up a list – anyone found one?

the figures advertised should be obtainable when driving on the road

dave, the current (NEDC) test will never achieve that. Hopefully the forthcoming WLTP lab test and RDE test (emissions measured on the road) will produce figures that are much nearer reality. The EC regulate all this and only they can sort this.

I have criticised this convo’s intro above for suggesting (implying) that emissions, as measured by Which?, are breaking limits as if the manufacturers are flouting regulations. I pointed out that there are currently no limits specified for the test cycle that Which? puts cars through. Only the NEDC test produces emission values that are judged against regulatory limits.

I do not side with manufacturers (I have no reason to) and like I imagine everyone else want to see real life emissions reduced and regulated. I was, therefore, very heartened to see that in the February issue of Which? Adrian has an article on emissions that places the blame mainly on the major culprit – the EC and its well-outdated NEDC test. This, together with what many might see as a resistance from car makers, gives a much more balanced view of the situation, and, more importantly, what is being done, and what needs to be done, to achieve more realistic information on car emissions (and, of course, fuel consumption).

I’d support a campaign to get the EC to ensure the WLTP and RDE tests are made the official tests as soon as practicable. I’d also support a campaign to get proper oversight of the “independent” test labs.

In addition I’d ptopose a campaign to reduce non-essential polluting vehicles in towns and cities, even if only at peak times. Reducing traffic (and traffic jams) would be a very effective way of reducing pollution. Parts of London already have broken a full years total allowance for NOx – in the first few days of the year. That cannot go on for the sake of people’s health.

Hi Malcolm,,,,,,,,,,,Happy to see you dont side with the manufacturers………..Also agree about the EU being the culprit however it was not the EU on their own…………The main culprit……………actually in my eyes they must be the epitome of reluctance to change

The manufacturers kept pushing the test systems into the shambles it became.
Way back,,,,,,,, the emissions were meant to be what we seen on the road and the Lab test was meant to be a simulation of road driving which today could not be further from reality but that doesnt mean that it didnt start off right………….nor does it mean that the EU volunteered to change the test indeed getting the EU to change anything is next to a miracle to behold
I’d be very critical of the EU and I make no secret of that……….I think we should never have joined as a full members but now we are there leaving may not be the right solution but more of knee jerk reaction and those are not good reactions to base decisions on.
However i do not wish to start political debate but simple wish to point out that I dont like Brussels but we have them so lets use them

However we’ll probably come together again in saying that the test did not move with the times or technology,,,,,,,,,,,,,,This can be fairly and squarely laid at the doors of Brussels
This allowed manufacturers to take advantage of the system…………Even those who do not have a cheat have an ongoing/continues low emissions mapped in for the type of driving being simulated……..They are not cheating,,,,,,,,,,,,,just about maybe???????,,,,,,,,,,,,I would say they are NOT cheating but then I would also say that they are as much to blame for this as the test.
They know they have made the vehicles fit the Lab tests………….That has became the norm

If this scandal stays to the fore and the manufacturers dont succeed in killing it you’ll probably get to see the reports of this as time goes past

So there are reasons why I’m a little adamant that the manufacturers carry a large part of the blame
They are far from innocent……..
I know I rabbit on a little but lets try this…………..I consider that some tell lies by saying nothing………..

I keep going back to being very critical of VW and accusing them of downright cheating whilst I always say that most others are not in the same boat…………..The VW cheat is so blatant and VW were embroiled previously in years gone by so I feel obliged to come down hard on VW

I know you have a test background
I’m on the other side of that coin……….
If in some of your tests you witnessed or overseen you now learned that????????????Samsung/Sony/Hoover/Hotpoint/WW/whoever had been operating a software cheat that made the machine great looking for the test but then once out in real life they switched on another 2kw element you let alone the customer would feel cheated
You were there you signed it off,,,,,,,,
That would be comparable to the VW cheat

Then lets say that like the car lab test the washing machine test has to have the same level playing field as it has to be and that the test is always the same combination of events
What if the manufacturers programmed in the most economic, low energy combinations of operations to achieve A****** but for those series of events only
The machines never change……….Same events in your house or mine…………same results
The machines never change…………..But when wifey goes and does her normal overloading (sorry girls) and wants a fast wash the machine then pleases her,the person
She is not worried about how many kwh or litres of water it takes that day……..Just get me the washing done and get it done yesterday
The machine is programed to please her,,,,,,,why??????????
Because when it comes to buying the next one and Mr Samsung done everything she wanted off it what will she buy…………Samsung
Just like many who posted here that they got excellent service and mpg from their VWs and dont care about all this pollution malarky,,,,,,,,Who cares about that anyhow,,,,,,,,,,,no one they know apparently………..They’re probably so pushy no one turns the word on them anyhow…
So the cars are the same
I’ll bet,,, and have done,,,, ever since you seen “DeeKay”appear Which that VW may be on their own on this one and if not if VW get more then one for company I’ll be surprised

But what I do know is that the cars,,,,,,,,,not just the test cars,,,,,,,,,,,,,all of some if not all model ranges dont have “a cheat” but they have a very precise set of rules that can make them a little better looking.
Everyone is distracted by the VW cheat but as I put it it cheats the road in order to get high mpg and bhp instead of simply cheating the test which seems to easier for folk to understand but is not correct.
VW didnt go to work in the morning to cheat the test………VW wanted better mpg and bhp than anyone else in order to sell their cars………a byproduct of the extremities of their actions would have them end up being caught for have a cheat
They simply could not ignore the test,,,,,,,,the test is a reality………..however they threw all the rules out the window
These other cars dont need to recognise the road and disable their EGRs etc………….They are not doing that
They never go to road/dirty mode………They just have a little cleaner map when driven in precise test fashion
We already know that there are drivers employed because they are good at getting the test simulation correct time after time but if you or I were to try it,,,,,,,,,,,not a chance
Bring the cars out the door and drive them up the real road in the same identical fashion and you’ll get the same results……………absolute,,,,,,,,,,no questions,,,,,,,,repeatable

I cannot say they have a VW style cheat……………I’ve waited years on that one breaking but I will say that a high % whilst not cheating as in having outright cheat software they have a nice set of characteristics that suit getting nice results

Again both you and call for various testing…………You call for changes……….I call for testing now to get now figures…………..Just now no one has produced any VW numbers outside of their original NEDC published…………you will say that that is the level playing field and if they cheated that is another story………….I’m surmising they are so bad there would be problems or repercussions if the real numbers were published……..
I like controversy in these matters because controversy brings things to the boil

What I have had in my eye’s via the latest Which emissions claims is verification that what I knew about is now pretty much in most of the industry
Now I know that you will say that they passed the test……..the test is final,,,,,,,,,so the test is wrong
What I am saying is slightly different
I’ll be fairly sure that if you take any of these very vehicles Which tested straight to the lab warm or cold they will pass the current emissions tests
Yet on an ordinary road drive they exceed the emissions requirements by quite a margin and some by multiples.
To me that is not the fault of the test……………The manufactures have adjusted themselves to fraud you and I
Given that it is an offence to cheat/rig the test via this software route are we not seeing some pretty close to the wire stuff here????????
Yes the EU has overseen it but I’m not so sure the EU were aware of the extent of the problems we are now seeing

I dont wish to argue or offend just debate if that’s okay

Which should be launching a campaign to force all vehicle manufacturers, to immediately invest in exhaust systems and modify older ones, which have disposable filters based on petrol consumption.
In other words when you fill up with a minimum of half a tank of fuel you replace a pull out/push in filter at the tail pipe.This would be left at the fuel station for disposal and your bill would record it had been changed to prove to a on spot check.
If the public want to stop their own death or others, by vehicle emissions, and all the other damage that it causes all over the world then a radical system must be found.
What about it WHICH

At the risk of making this thread look slightly repetitive, I want to add my voice to the calls for Which to make all of their emissions test data available. A nice big table would suit me.

First my apologies if I duplicate anything already said on this thread, I have not read through it fully yet.
In my opinion I think the fuel manufacturers/processors should be involved here too, assuming they can. I’m not a science bof, but can the diesel be produced in such as way as to reduce/remove the possibility of emitting these NOX/NO2 fumes. As we had in the ’80s a purge on lead-free petrol, can this be done with diesel. If so, lets start a campaign “NO2 free Diesel”, or something similar.
Thoughts, comments, ideas or suggestions most welcome.

The NOX is a result of the function of compression ignition
The fuel has already got a load cleaned and lighter
It is nearing 28sec heating oil but with retardant as heating oil is a little too quick off the mark in such cylinder conditions
The fuel manufacturers and the engine manufactures have moved quite a way in reducing emisions but the problem is the lean burn nature of the diesel engine
There will not be a NOX FREE DIesel
If it gets to this level of pressure we my find,,,,,,,,,I’m not sure,,,,,,,,,,that we have to opt for the cleaner fuel rather than the more economic engine
I have a SX4 1.6 petrol……….112 bhp…….45mpg……..all day every day and if on a run over 50 no probs
anything wrong with that????????
I also have a Panda Diesel,,,,,,,,,,,,60 to 65mpg…………A little more servicing yes but a little more economy yes
I dont know where this is all leading,,,,,,,time will tell,,,,,,,,,but holding to the past may not be the answer


The short answer is the N in the NOx comes from the air and not from the fuel, so it is not easy to get rid of it.

About 80% of the air used in combustion is Nitrogen (N) and about 20% is Oxygen (O). (There are other gases present too, including, of course carbon dioxide (CO2), but we won’t worry about those …)

If you heat nitrogen and oxygen together, for example when you burn fuel in a piston engine, then chemical reactions to produce oxides of nitrogen can take place – so variants of NOx, such as NO and NO2 can be produced.

In practice, the Oyxgen will also be needed for the combustion of any hydrocarbon fuels, e.g. petrol or diesel, but if there are both high temperatures and an excess of oxygen, then a lot of NO can be produced.

Whilst lean burn and economy are fine for the pocket they are not fine for our lungs
Yes there are ways but they are mostly add ons to clean diesels up……The add ons to the diesels have all been around for a few to 20 years and are far from reliable……..As a matter of fact I wish I could be as sure of staying alive to I am 90 as I can be of EGRs failing and DPFs blocking
Both petrol and diesel can be made to be fairly clean but if they stop chasing this lean burn nonsense petrol has no trouble having at least a 90% success of its CAT and EGR if it even has an EGR of lean burn is left alone for the life of the vehicle
Is it not the case that life and health are more important than mpg


I agree:

High mpg implies low CO2 but high NOx

Lower mpgs suggest higher CO2 but low NOx

So we need to find the “least worst” option…

Low CO2 and low NOx are desirable outcomes – but tend to be mutually exclusive.

Why haven’t Which just featured the latest emissions findings against their car reviews, instead of producing yet more tables that add to the confusion? And Which says all but seven vehicles don’t meet the required emissions standard. So what do they do-list the worst offenders instead of the seven that do comply. Er why??

This link is to an article on lead additives in petrol which is obviously not a current problem of cars however it is a story of poisoning people via combustion. It also mentions the lead in our environment and the current dangers.

It might also bea warning that what commercial companies do are not always in the interests of humankind – in this historic instance General Motors.

The correlation of cause and effect is one of the best fits [if the research is true] that you would ever wish to see.

“what commercial companies do are not always in the interests of humankind”. This implies, but perhaps I’ve misinterpreted, that GM and petrol companies had knowledge of the effect lead tetraethyl had. I doubt that. Our knowledge of harmful substances grows with experience – arsenic in make up and green wallpaper, asbestos used for insulation, for example. The link with crime, however, is interesting.

By the way, do you think Which? will ever get round to compiling a database of defective products?

Oh Yes GM, Ford etc had all the knowledge as had the petrol companies…….Long before such debates became public
Then when we were phasing out leaded petrol the die hards kept on buying it like their cars were going to go up in a puff of smoke if they used lead free
The car manufacturers?????????
In exactly the same way they would not fit seat belts
The car industry is a little like the tobacco industry
Even when the evidence is all against them they keep fighting
Even after the case is proven against them they keep defending their innocence
Malcolm the car industry is second only to big tobacco and they will never give in……they will never stop cheating………….they will never tell the truth
When we have beat this one,,,,,,,nuclear is next

John says:
24 January 2016

The public have been lied to by the motor industry in order to buy more cars which do not come up to emission standards in normal driving.This is a fraud and this is criminal action by the industry. Those guilty of ordering such policy at board level should be in court and imprisoned when if found guilty.This is the only way management will change policy. The workers should not be used as scape goats for the management.

Alex Lothian says:
24 January 2016

It is, in my mind, ridiculous that car manufacturers have put profits first, and attempted to circumvent the regulations, by doing so have put their customers as well as the environment at risk. These companies must be brought to book.

Alex Lothian says:
24 January 2016

I think it is ridiculous that in order to gain profits car manufacturers have combined to circumvent the regulations that are in place to protect both the public and the environment, placing their own customers at risk. It is time that the companies were held to account, fined appropriately, and where necessary named and shamed.

The only regulatory limits motor manufacturers must comply with are those set by the EC and measured according to the EC test. Unless they falsify the figures or do not follow the procedures allowed by the tests I do not see where fraud or criminal culpability is involved.

The answer is to have a proper test, properly administered with appropriate emissions limits with the independent test laboratories properly supervised. Then we should get figures that we can both rely on. and that are meaningful.

The EC control the test and the limits. They are substantially to blame for not keeping the test up to date and stringent.

I hope the WLTP and RDE will address this problem more effectively.

I cannot see any logic for having a different NOX limit for petrol & diesel. The Petrol Honda Civic’s 0.0027 result is only 4.5% of the 0.06 limit.
The European Commision wants to up the diesel limit, ridiculous.

I presume the different limits reflect what is considered to be achievable under the NEDC test. Just as CO differs.
The results from the NEDC test, and the limits based on it, are almost irrelevant if they do not give data that can be achieved in real driving – on the road. It will be interesting to see what the RDE (real driving emissions) trials, that have just started, reveal.

I’m not worried about “Achievable”
Achievable does not clean the air up
Less traffic and less dirty traffic cleans the air up
If your going to ask VW what is achievable what’s the answer going to be
I was in that industry for years and they would run right through you for a short cut if you gave them that chance
Wow I can just imagine back then someone coming in the door and say the EU wants to meet with representatives form all the manufacturers within the industry to see what is achievable…………..The comments would have been beyond writing here and would have mocked the EU to the lowest…………..**** me they mocked anyhow

There is no point in any situation in setting limits that cannot realistically be achieved. Targets maybe. As I have said before, if we really want to reduce emissions we should bite the bullet and also reduce polluting traffic in towns and cities. But just how serious are we? It is like being allowed to pay to enter an ultra-low emissions zone with a polluting vehicle; so you can help poison the atmosphere providing you have the money.

I accept the point about the manufacturers but it is up to the EC to decide the limits and then to impose them. I hope they will properly consult, and use information that has been properly derived, so that we move into realistic territory where emissions can be genuinely minimised and achieved on the road.

I believe that there has to be more than targets to achieve progress. It is amazing how much more can be achieved if there is pressure. We know that the nitrogen oxide emission limit is lower in the US than in Europe, so perhaps current European limits are perfectly achievable.

If manufacturers were taxed according to the emissions of the vehicles they produces there would be a good incentive to do better.

It may well be that lower emissions could be generally achieved in Europe. It is up to the legislators to set the limits below which cars will receive type approval. That is the EC’s job. So should we not be getting BEUC and/or all the European consumers’associations to make appropriate representations to the European Commission?

I believe that recommendations for emissions limits should come from specialist research institutes and universities that have the expertise. I would very much welcome consumers associations having more input as independent assessors of what is being achieved. Had they been involved, the Volkswagen ‘cheat’ might have been detected sooner and there could have been pressure to eliminate modifications of cars (taping up doors, over-inflating tyres, etc, etc) prior to official testing.

In another Conversation we have heard of the ‘circular economy’, one of the aims being to ensure that household appliances are properly recycled rather than ending up in landfill. Consumers’ organisations need to make an input to prevent the circular economy also being used as a mechanism to prevent us being pushed in to a programme of regular replacement of goods, as currently being done with cars via personal contract purchase.

“emissions limits”. Would you like to point to these specialists who understand engine technology, techniques, and achievable objectives? I would expect that the EC’s job is to do this. Perhaps Which? could find out just how the EC comes up with its recommendations.

As far as personal contracts on cars, i always take the view that if someone else proposed financing my purchase they will cost me more than I would pay if I funded it myself, even with a loan. however manufacturers offer incentives to purchase through their own loan facility. I recently had to buy a new car. The manufacturer offered around 11% off the list price if I took out their loan, which i did. As soon as the car arrived I cancelled the loan agreement but the “contribution” stayed. Quite a common practice that the dealer said to use.

At least cars purchased under personal contracts come back onto the used market for someone else to pick up; they are not scrapped. What does bother me is the scrapping of potentially good domestic products simply because they have inadequate durability for the price and/or they are not economically repairable either through lack of spares, unreasonably expensive spares or difficult and costly labour.

I expect the EC to coordinate emissions limits and testing programmes, but engine design and achievable objectives are not the only considerations. It is important to consider health benefits and other sources of pollutants, climatic conditions, etc. I want to see decisions that affect our lives made using up to date and comprehensive information.

Sorry but my car achieves closer to the manufacturers mpg than which’s figures. I have a corsa diesel, but the 75hp version. this is supposed to be less efficient than the 95hp version that which measured yet in my mainly motorway driving i get close to 80 mpg. i think the manufacturer claims 82 mpg. if i drive between 60-65 mpg i hit the manufacturer figures. i have used manual measurements too and not just the trip computers. no matter how i drive i dont get less than 75mpg.

Why are which not actually naming the cars that failed their tests. If which are 100% sure they’ve got the facts right then they should be confident enough to ‘name and shame’

Which?’s test is not the same as the official EC test that produces emissions values for comparison against EC limits. It “drives” the car differently from the official test, and emissions are crucially affected by the way the car is driven. What Which? have done in the February magazine is list the worst offenders in their tests – both petrol (5 for NOx, 10 for CO) and diesel (10 cars).

Which? is not helping here by referring to cars breaking the emission limits when, as yet, no limits exist for the test they do. It should make this clear rather than confusing readers who may not be familiar with the details of car approvals.

I support the calls posted earlier for Which to list the emissions of all cars they have tested.
And because NOX emissions seem to me to be the most harmful, list in order of those.
Because of NOX testing results, are there now only 7 diesel models of the 153 tested (page 21 Feb mag.) awarded Best Buy status? It is impossible to check this because Which car reviews data do not allow sorts using emissions criteria.
Finally, why is Which not campaigning for car tax (VED) to be based on NOX?

It is rather a curious animal Which? .

For most of us it is primarily a product testing body and information provider. However it has now, with other organisations, gone to the stage of posting calls to sign up for scores of causes and complaints. And of course it has become rather more commercial which makes for some difficulties in commenting on others competing in the same market.

This was probably something that the founders appreciated when they wrote the Articles of the Consumers’ Assoc as to what it can and cannot do.

IMO for Which? to campaign on tax matters directly would perhaps gain opposition from members of the public. Which? might more legitimately be campaigning against TIPP terms that harm consumers and letting the UK public know what is going on. Much less dangerous to the image.