Extremely polluting Nissan and Renault diesel cars still on sale, data reveals

Cars that emit up to 18 times the official NOx limit in real-world conditions are still being sold, 20 months after the emissions scandal broke and amid an ongoing air pollution crisis.

The continued sale of highly polluting diesel cars is surprising, said Nick Molden, at Emissions Analytics: “The technology to clean up diesel emissions has existed for quite a long time.”

Read the full article from The Guardian

Toxic times for diesel

Diesel has had something of a rough time of it over the past 18 months. It started with the Volkswagen ‘Dieselgate’ scandal that broke in September 2015, while more recently there have been concerns over nitrogen oxide (NOx) emissions and air quality in general, especially in city centres.

According to Nick Molden, CEO and founder of Emissions Analytics – a company that tests car emissions in the real world – some meet and can even beat the limits prescribed by the Euro6 emissions regulations, while others, according to Emissions Analytics’ data, emit 20 times the NOx that they should.

Read the full article by James Richardson at Businesscar

The Sunday Times: “UK approved Fiat’s ‘dirty diesel’ engine”

In an article dated January 15 2017 by Jonathan Leake, Environment Editor at The Sunday Times, Emissions Analytics’ CEO and founder Nick Molden is quoted as saying: “When a vehicle passes laboratory tests but shows such a different performance on the road you have to be suspicious about the technology.”

This comment was made in response to the news that Fiat Chrysler are being investigated by the US’s Environment Protection Agency and the UK’s Department for Transport due to significantly higher real-world NOx emissions than those emitted during laboratory testing.

The EPA has issued a ‘notice of violation’ to Fiat Chrysler – listing alleged devices including timers which are said to switch off parts of the emission control system after the engine has run for the short time needed to conduct tests -for failure to disclose auxiliary emission-control devices, or AECDs, which is a violation of the Clean Air Act.

Emissions Analytics found that Fiat’s 500X MultiJet with a 1.6-litre diesel engine, emitted 14 times above EU and UK limits. The Fiat Doblo van was even worse, with emission 17.8 times above the legal limit, even though it has passed official tests.

For more data on Fiat, and other vehicles visit the EQUA Index.

Can hybrid electric vehicles beat diesels on mpg?

Hybrids have always had a miles-per-gallon advantage in urban driving but new EQUA Index data shows that they are gaining on diesels in motoway or highway driving and, if current trends persist, hybrid electric vehicles (excluding plug-in hybrid electric vehicles) are set to take the lead in 2017.


The dotted trend lines in the above graph, representing motorway mpg for diesel vehicles and gasoline hybrids tested by Emissions Analytics, are converging. While the downturn in diesel mpg may be due to a change in manufacturers’ focus from fuel economy to NOx emissions, what is more striking is the improvement in gasoline hybrid performance on the motorway as a result of technological advances.

The step change in technology is even more noticeable when European EQUA data is compared to North American EQUA results. The graph below shows gasoline hybrid performance in the US is particularly impressive on our combined cycles. With this level of fuel economy it seems unlikely that diesel vehicles will ever make a significant impact on market share in the US. With the mpg penalty of some NOx aftertreatment systems, perhaps it was to gain a fuel advantage over hybrids that Volkswagen resorted to using a defeat device when bringing their diesel models to the US market.


Another noticeable effect of the different product mix in the US is the level of carbon monoxide emissions. Both regular gasoline cars and gasoline hybrids have much lower CO emissions than their European equivalents, with regular gasolines 30% lower and gasoline hybrids 64% lower. This is despite the fact that the US have a less strict limit, at 2.1g/km, than the EU’s, 1.0g/km limit.

When we last wrote about hybrid vehicles back in October 2014, we concluded they were delivering “good but not best-in-class fuel economy, but [were] typically the cleanest, and if you are a light-footed, congested town driver, they are ideal.” Two years on hybrids, particularly in the US, have really upped their game. They are still a cleaner drive than a diesel and may soon offer better fuel economy wherever you drive them but heavy-footed drivers should still exercise caution.

Are diesels done for?

As the government loses a second high court ruling brought by ClientEarth, many are now sounding the death knell for diesel cars. Not so fast, says Emissions Analytics, diesels can be clean and govenments are highly unlikely to give up the greenhouse gas advantage of diesel in the short- or medium-term.
Since the introduction of Euro 6 in September 2014, manufacturers have been forced to improve their after-treatment systems to meet the stricter legislated limits for NOx. Exhaust Gas Recirculation, Lean NOx Traps, and Selective Catalytic Reduction technologies have been employed as part of a complex strategy to reduce tailpipe emissions. There have been variable successes, with some achieving the regulated limits even in real-world driving and the worst more than 20 times the legal limit. Overall, average NOx emissions from Euro 6 diesels are down 55% compared to Euro 5s.

Nonetheless, there is still the fact that many new cars do not meet the legislated limits in real-world operation. Our data shows NOx emissions are on average 4.3 times over the limit for Euro 6 cars and, after a period of improvement, this Conformity Factor is rising. This is the heart of the issue, as to whether diesels are the major and unavoidable cause of poor air quality in towns and cities.

Consequently, there have been many suggestions made to combat the problem of dirty diesels. These range from the London Mayor’s T-charge, to a diesel scrappage scheme, to a total ban on diesel vehicles in certain zones. However, Emissions Analytics’ data shows that modern diesels in their own right can be clean.

Since the launch of the EQUA Air Quality Index six months ago, twelve cars have how achieved an A-rating including the latest Volkswagen Tiguan, meaning it has met the 0.08g/km limit in real-world driving.


This proves that diesels can be clean and the reason most are not is down to a failure of regulation and enforcement and not the technical impossibility.

There is also the issue of CO2 emissions to be considered. Despite Donald Trump tweeting that climate change was, “created by and for the Chinese in order to make U.S. manufacturing non-competitive,” the British government has an empirical view on global warming and stands by its commitment to cutting its carbon footprint. Would ministers give away the 16% CO2 advantage – according to Emissions Analytics’ testing – diesel has over gasoline for the same distance driven in real-world operation, until there is a viable alternative.

In the future electric and hybrid vehicles may deliver the CO2 advantage required, as well as greatly reducing, or eliminating, NOx and other harmful emissions, at which point diesel powered engines for passenger cars may come to the end of the road. However, with a share of the market of less than 2%, there is still a way to go for these vehicles. Until then, Emissions Analytics’ data strongly suggests the policy focus should be on sorting the clean from the dirty diesels and incentivising manufacturers to bring forward clean technology.

The latest EQUA Aq Index results are available online

Emissions Analytics launches EQUA Carbon Monoxide Index

Emissions Analytics is pleased to announce the launch of the EQUA CO Index. The second in the EQUA Index series, EQUA CO looks at whether carbon monoxide regulations are being achieved in real-world operation.

Potentially fatal for humans as well as damaging to the environment, carbon monoxide is generally considered a problem primarily confined to gasoline vehicles. Regulations distinguish between the fuel types, with diesels having a more stringent but, due to their technology, easier to achieve limit of 0.5g/km. Gasoline vehicles have to meet a more generous 1.0g/km limit which is typically achieved using a three-way catalyst. Therefore, the regulations are not technology neutral and allow gasoline vehicles to emit twice that of diesels and still be compliant.

In the same way that Emissions Analytics rates emissions of NOx from diesels, gasolines and hybrids with a single scale on the EQUA Aq Index, the EQUA CO Index awards a universal rating regardless of fuel type. Thus despite the regulations setting different boundaries, the EQUA CO Index allows comparisons between vehicles. The A++ to H ratings are set as follows:


Using these classes, a diesel car awarded an A to A++ meets the regulated level even in real-world driving, whereas a gasoline vehicle with a C to A++ meets the regulated levels for this fuel.

Of the 734 vehicles currently on the EQUA CO Index, 96% emit the regulated amount of CO or less. However, there are some interesting exceptions. Several Mercedes C-Class diesels are over 0.5g/km, out of a small number over the limit. Additionally, 8% of gasoline vehicles, that is 24 models tested by Emissions Analytics, do not meet the regulated limit, with one outlier being more than six times over. If the regulations were to change and gasolines had to achieve the same, stricter standard as diesels, the number of cars failing to reach this standard would increase to 20%. Of the hybrid vehicles tested, all achieve the regulated limit apart from the Mitsubishi Outlander which scored a D-rating when not running on its electric engine.

The vehicles tested by Emissions Analytics are all  run on our standard real-world cycle. The tests are conducted by a small pool of highly trained technicians and the vehicle and testing equipment is carefully prepared to make sure it is fully warmed up and in the manufacturers’ default settings.


The data shows that illegal levels of carbon monoxide are not as prevalent in real-world driving as excess NOx from diesels. However, given the toxicity of CO, this is a situation that needs to be monitored. This could become particularly relevant if there is a market shift away from diesel towards gasoline as a result of dieselgate and other emerging regulations and taxes. Emissions Analytics will continue to keep a watchful eye on on-road vehicle performance, checking it against official certification and publishing the results online on the Carbon Monoxide page at the EQUA Index site.

Subscriptions are available to the Emissions Analytics database. Contact us for details.

The end of the road for dirty diesels?

We have been listening to the proposals to discourage ‘dirty diesels’ by cities across Europe, and read with interest the statement from the Society of Motor Manufacturers and Traders (SMMT), speaking up in favour of the diesel car. In our opinion, the evidence from real-on-road tests speaks for itself.

Our research shows Euro 5 standard diesels and earlier are indeed ‘dirty’. They produce high levels of NOx which is harmful to human health. Emissions are particularly bad in urban environments because NOx emissions correlate more closely with incidences of acceleration than speed, thus the stop-start nature of city driving exacerbates air pollution. And, it is made worse by the high number of older diesel buses, taxis and delivery vehicles in the urban environment.

To help combat this problem, the legal limit for NOx emissions was reduced to 0.08g/km with the introduction of the Euro 6 standard for passenger cars, effective from September 2014. We tested a number of the earliest Euro 6 diesels on the market and found that they produced levels of NOx which were seven times above the legislated limits. You can read more about it in the ICCT’s 2014 report, to which EA contributed data.

However, our latest tests show that many newer Euro 6 diesels are showing marked improvements, with NOx levels averaging 2.5 times above the legislated limit. In addition, great strides have been made to clean up new buses and the NOx emissions are now very low from many of these vehicles. Another concern with diesels is the emissions of particulates which are linked to heart and lung disease.  However, this issue was addressed with the Euro 5 standard which saw the addition of diesel particulate filters to the exhaust system, which has significantly reduced this problem.

Automotive manufacturers have been investing in NOx abatement technologies and strategies in anticipation of the forth-coming legislative changes which will require an element of real on-road testing, known as Real Driving Emissions. In future it will no longer be sufficient to simply pass the test, manufacturers will also have to demonstrate that their vehicles also comply when driven in the real world.

This can only be to the benefit of urban air quality and thus we agree with the SMMT in that a simplistic ‘demonisation’ of new diesels is not correct. In fact, careful attention needs to be paid to other technologies creating emissions increases, such as direct injection gasoline engines.  Nevertheless, there are issues with diesels that are not captured by the regulations, for example the proportion of NOx that is emitted as NO2, the more harmful component.  Our research shows that this proportion can be as high as 90% in urban driving, much higher than generally acknowledged.

Emissions Analytics has been leading research in these areas, for example with Imperial College London through the Air Pollution Research in London group, to ensure that the clean-up of diesel engines continues to translate into reality.