In depth: how carmakers performed in the first wave of real world tests

Explore the findings of Unearthed's real driving emissions investigation, company by company

Since late 2015, all new diesel cars are supposed to emit a maximum of 80mg/km of nitrogen oxides (NOx), under an EU-wide standard called Euro 6, which is intended to limit air pollution from vehicles. Historically, the way the EU checked cars’ emissions was through laboratory tests. But by 2015 it had become clear that these tests were inadequate, because cars were emitting much more NOx on the road than in lab tests. In response, the EU brought in a new test, which examined how cars performed in the real world.

To give car companies time to adjust to this new testing system, the EU initially introduced a real driving emissions (RDE) limit that was more than double the Euro 6 standard, at 168mg/km for diesel cars. This came in on 1 September last year. For a “monitoring period” lasting from April 2016 to 1 September 2017, there was no limit at all on how much NOx cars could produce in the real driving emissions tests: while car companies had to test their real-world performance, the only thing that counted for Euro 6 accreditation was the laboratory tests.

Our investigation has shown that many of the new cars brought out during the monitoring period had real-world emissions far above the Euro 6 limit – and this is perfectly legal.

We found there was a huge variation in how models performed: here, in detail, is what our investigation found about each company.


BMW brought out more than a dozen diesel models during the real driving emissions test monitoring period, including a range of 5-series saloons and estate cars and X3-series SUVs.

Across the board, these cars were among the best performers in the RDE test data Unearthed obtained. In every test recorded, overall average NOx emissions were not only below the current RDE limit of 168mg/km, but also the Euro 6 lab-based limit of 80mg/km.

In all but one case, urban emissions, testing how cars perform in urban driving, were also below 80mg/km.

The highest average emissions recorded were 49mg/km (0.6 times Euro 6), in a test on the 530d xDrive station wagon. The highest urban emissions were 83mg/km, in a test on the 540d xDrive station wagon.

A BMW spokesman said the results “reflect the highly effective combination of [NOx Storage Catalyst and Selective Catalytic Reduction] which is being rolled out across our model range this year”.


Citroën has released three diesel models that were put through type approval between April 2016 and September 2017: the C3, the C3 Aircross, and the C4 Cactus.

All the Citroën vehicles tested were fitted with selective catalytic reduction (SCR) technology, which is considered the most effective technology for reducing NOx emissions from diesel vehicles. Despite this, every vehicle produced NOx emissions in excess of 168mg/km on the road (the “not-to-exceed limit” for real driving emissions that came into effect from 1 September 2017).

The highest emissions were for the C3 Aircross, which came onto the market in June last year. Citroën reported four tests on two variants of the Aircross, with NOx emissions ranging from 280mg/km up to 350mg/km (or 4.4 times Euro 6).

The C4 Cactus recorded NOx emissions of 335mg/km (4.2 times Euro 6), while tests on C3 variants produced emissions ranging from 184mg/km to 315mg/km (3.9 times Euro 6).

A Citroën spokesman said the models were all tested during the monitoring period and were “not required to comply with any NOx limits for RDE testing”.

He added that the company has made a “voluntary commitment” that all “Euro 6d-Temp” vehicles it brought out (meaning vehicles that do have to pass the RDE test) will emit no more than 1.5 times Euro 6 (or 120mg/km for diesels). This is tougher than the current RDE limit, and will not become the mandatory limit for new models until 2020.

However, he said that late publication of the EU’s latest RDE regulations had “delayed our Euro6d-Temp product launches”. He added: “Our first three [Euro 6d-Temp] type approvals (2 diesel and 1 petrol) were obtained at the end of July 2017 and we achieved NOx conformity factors below 1.5.”


Fiat has only had one new diesel model of car approved for sale since real driving emissions test rules came into effect, but the on-road emissions for that model were strikingly high.

RDE results for the 1.6l diesel Fiat Tipo – which is not fitted with SCR – show its urban NOx emissions were a whopping 753mg/km – 9.4 times the Euro 6 limit and by far the highest of any car covered in Unearthed’s investigation. Its overall average emissions were also the highest of any car covered in this investigation, at 561mg/km, or 7 times the Euro 6 limit.

The only other diesels Fiat has put through type approval since April 2016 are SCR-fitted versions of its 2.3l Ducato van. Fiat has reported results from RDE tests on two Ducatos. One recorded on-road emissions that were well below the current RDE not-to-exceed limit, both on average and in urban driving. The other recorded average emissions of 155mg/km, just under the current NTE limit. But its urban emissions were 280mg/km, or 3.5 times Euro 6, which would cause the vehicle to fail an RDE test if it was being put forward for approval today.

Fiat declined to comment.


Ford has only put two diesel model updates through type approval since the real driving emissions test came into effect: its 1.5l EcoSport SUV, and the 1.5l diesel model of its bestselling 2017 Ford Fiesta.

The EcoSport stayed within the current RDE not to exceed limit of 168mg/km (or 2.1 times Euro 6) in both tests on the vehicle reported by Ford, both on average and in urban driving.

However the flagship Fiesta did not, with one of the two tests showing urban emissions of 242.5mg/km (triple the Euro 6 limit) and overall average emissions of 261.8mg/km (3.3 times Euro 6).

A Ford spokesperson emphasised that both vehicles had been certified before 1 September 2017, when the not-to-exceed limit became mandatory, and were legally compliant with the standards in force at the time they were approved.

She added: “Due to the long lead time in the development of vehicle powertrains it was not possible to launch the Fiesta to the then future requirements. The vehicles have been engineered to the original targets that they were designed to meet.

“We do not normally [discuss] future product plans publicly, however given that it is now possible to obtain certificates for the Euro 6d WLTP [Worldwide Harmonised Light Vehicles Test Procedure] and RDE step 1 regulation, we will meet the regulatory deadlines and standards as legislated.”


Hyundai put only two diesel vehicles through the real driving emissions test during the monitoring period, both versions of the 1.6l i30 hatchback. In every test the vehicles’ average and urban NOx emissions were above the limit that would be allowed if they had been tested after the monitoring period ended.

The company recorded two tests on a high power version of the i30. The car’s overall average emissions ranged from 224mg/km (or 2.8 times Euro 6) up to 251mg/km (3.1 times Euro 6); its urban average emissions ranged from 186mg/km (2.3 times Euro 6) up to 335mg/km (4.2 times Euro 6). A further test on the lowest power version of the i30 recorded average emissions of 191mg/km (2.4 times Euro 6) and urban emissions of 261mg/km (3.3 times Euro 6).


Kia has put two new diesel models through the real driving emissions test since the monitoring period began: the 1.4l Kia Rio and the 2.2l Kia Stinger.

The Stinger is a brand new car, and diesel models only became available in the UK at the start of this year. RDE test results show Kia put two versions of the Stinger, each with a different type of emissions control device, through type approval for sale in the EU.

The first was put through the RDE test in April last year. It was fitted with a Lean NOx trap to control NOx emissions, and its emissions were well over the 168mg/km limit that came into force in September. Overall average emissions were up to 255.5mg/km (3.2 times Euro 6) and urban emissions were up to 352mg/km (4.4 times Euro 6).

Then, in early September, Kia put another version of the Stinger through RDE testing, this time fitted with SCR technology. NOx emissions this time were well below the not-to-exceed limit, and also below the original Euro 6 limit. The highest overall average emissions for this car were 47.2mg/km (0.6 times Euro 6) and the highest urban emissions were 63.7mg/km (0.8 times Euro 6). This model is being marketed as meeting the Euro 6d-Temp limit.

A Kia spokesman said that all diesel Stingers coming into Europe (including the UK) were the SCR-equipped version with low NOx emissions. But the company declined to answer questions about whether or where it is marketing the high-emission Stingers that do not have SCR systems, or to explain why it put this version through the process of being approved for sale in Europe. The Stinger is a “global car” with versions on sale in Europe, Russia, the Middle East, South East Asia, Australia, and the US.

The 1.4l Kia Rio exceeded the 168mg/km standard in two out of three tests, with the low power version recording NOx emissions of 218mg/km (2.7 times Euro 6) and the high power version emitting up to 184mg/km (2.3 times Euro 6).


Mercedes-Benz only put two diesel models through the type approval process during the monitoring period, the S400d and the S350d, but their performance in the real driving emissions test was among the strongest of all the results Unearthed analysed.

In every test, the 2.9l vehicles recorded NOx emissions well below half the on-road limit for new cars going through type approval now. Overall average NOx emissions for the S350d ranged from 13mg/km (0.2 times Euro 6) to 35mg/km (0.4 times Euro 6), while urban average emissions ranged from 29mg/km (0.4 times Euro 6) to 74mg/km (0.9 times Euro 6). For the S400d, overall emissions were between 15 and 31mg/km and urban emissions were between 30 and 73mg/km.

Mercedes is also one of the first manufacturers to have brought out diesel cars type-approved under the Euro 6d-Temp rules that became mandatory from September last year: the CLS 350d 4Matic and the CLS 400d 4Matic. Real driving performance for these cars was similarly strong, with the CLS 350d producing average emissions of between 4.8mg/km and 21.4mg/km, and the CLS 400d producing emissions of 18.1mg/km.


Nissan put two diesel models through type approval during the RDE “monitoring period”: a 2l version of its X-Trail SUV, and a 1.5l Nissan Micra.

Neither was fitted with SCR technology, relying instead on NOx traps to control NOx emissions, and all recorded on-road emissions above the limits that have been in place since September.

The 2l X-Trail was among the highest-emitting vehicles in the test results seen by Unearthed. Overall average emissions were up to 371mg/km (4.6 times Euro 6) for the high-power version tested, and up to 265mg/km (3.3 times Euro 6). Urban emissions were even higher: up to 437mg/km (5.5 times Euro 6) for the high-power version, and 404mg/km (5.1 times Euro 6) for the low-power version.
The Micra stayed narrowly within the current RDE limit for overall average emissions, but exceeded it in urban driving, with urban emissions of up to 255mg/km (3.2 times Euro 6).
Nissan declined to comment.


Vauxhall (known as Opel in mainland Europe) has released several diesel models since RDE monitoring began in April 2016: the 1.6l Crossland-X, the 1.6l Grandland-X, the 1.6l Insignia Grand Sport, the 2l Insignia Sports Tourer, the 2l Grandland-X, and two variants of the 2l Insignia Grand Sport.

All but the the 1.6l Grand Sport were equipped with SCR technology, but the emissions results were mixed.

All the cars with 1.6l engines had emissions in excess of 168mg/km in at least one test, with the highest average emissions being 388mg/km (4.9 times Euro 6) for one test on the 1.6l Crossland-X.

The 1.6l Grand Sport performed worst in urban driving, with emissions of up to 340.8mg/km (4.3 times Euro 6).

However, the cars with 2l engines all stayed within the current 168mg/km limit for real driving emissions, and in some cases had emissions lower than the lab-based 80mg/km Euro 6 standard. The best performers were the 2l Insignia Sports Tourer, with average emissions of no more than 39.4mg/km (0.5 times Euro 6) and the 2l Grandland-X, with emissions of no more than 35.5mg/km. The Grandland-X has been approved as a Euro 6d-Temp vehicle.

An Opel/Vauxhall spokesman said all its cars “comply with the legal requirements”, adding: “We are constantly improving the emission performance of our cars. The excellent results we achieve today with the most modern technology clearly prove the success of our ambitious strategy. And we will not stop. One example: From September 2018, all new diesel powertrains will use SCR.”

He continued: “Opel has started rolling out Euro 6d-Temp and model after model will follow. We are proud to even have some Euro 6b and 6c Diesels that clear the 2.1 [times Euro 6] threshold today.”


Peugeot put four diesel models through the type approval process during the monitoring period: the 1.5l 208, the 1.5l 308, the 2l 308 and the 2l 3008.

The Peugeot cars were all fitted with SCR technology to reduce NOx emissions, as well as a diesel oxidation catalyst (DOC) and particulate filter. The NOx emissions produced in RDE testing were among the lowest seen in Unearthed’s analysis.  

In every test, the total average emissions for the Peugeot cars were comfortably lower than the original Euro 6 standard of 80mg/km, and well below the RDE not-to-exceed limit that came into effect in September 2017 (which allows cars to emit up to 2.1 times the Euro 6 standard on the road). Total average emissions in the Peugeot tests ranged from 14mg/km in one Peugeot 208 test (0.2 times Euro 6) up to 51mg/km (0.6 times Euro 6) in one Peugeot 3008 test.

Urban emissions were generally slightly higher, but in all but one test were still lower than the original Euro 6 standard of 80mg/km.

A Peugeot spokesman said the vehicles were of the “latest Euro 6 generation”, but due to a delay in publication of the EU’s latest RDE test regulations and “in order to remain on track” Peugeot had originally type-approved them under the monitoring period rules (which do not impose a not-to-exceed limit for the RDE test). He added that these “diesel applications are now re-type approved to Euro 6d-Temp” – the latest standard, under which models have to stay within a 168mg/km not to exceed limit in the RDE test.

He added that Peugeot has a voluntary commitment that all its diesel vehicles approved under Euro 6d-Temp will emit less than 120mg/km NOx (or 1.5 times Euro 6). This is a tougher standard than the current RDE limit, and does not become a legal requirement for any vehicles until 2020.

However, the company was “disappointed” that late publication of the latest RDE regulations had “delayed our Euro 6d-Temp product launches. The spokesman continued: “Our first three type approvals (two diesel and one gasoline) were obtained end of July 2017 and we got NOx conformity factors below 1.5. The test values produced under the RDE testing conditions for the mentioned Peugeot models with the latest Euro 6 diesel powertrains clearly provides a proof to the above statement.”

Renault Group

Renault Group (which has two brands in Unearthed’s analysis – Renault and Dacia) stands out for several reasons: it secured type approval for a relatively large number of new diesel engine types during the real driving emissions grace period of April 2016-September 2017, none of them were fitted with SCR technology, and all of them produced on-road NOx emissions so high they would not pass an RDE test if they were put forward for approval today.

Renault Group type approved 14 “families” of new diesel vehicles during the RDE monitoring period. All but two of the 14 vehicles tested exceeded the Euro 6d-TEMP not-to-exceed limit of 168mg/km for their overall average emissions, with several among the highest emitters of all diesels approved during monitoring.

The worst overall emissions were recorded for the Renault Scenic Energy dCi 95 (a family that also includes the Scenic Energy dCi 110 and the Grand Scenic Energy dCi 110) at 396mg/km – 5 times the Euro 6 standard – the second-highest seen in Unearthed’s investigation.

There were only two tests in the Renault Group data that stayed within the Euro 6d-Temp limit for overall emissions – the Scenic Energy dCi 160 and the Kangoo Energy dCi 110 EDC – but both of those vehicles exceeded the limit for urban driving, at 250mg/km and 191mg/km respectively.

Several of the worst urban NOx emission results found in Unearthed’s investigation were for Renault vehicles, including the Megane Energy dCi 160 EDC, which recorded urban emissions of 388mg/km, or 4.9 times Euro 6.

A Renault Group spokesperson said that SCR technology will be fitted to all of the group’s diesel passenger cars and light commercial vehicles by September 2019, the deadline after which no new cars can be sold unless they have passed an RDE test.

He emphasised that all of the diesels in Unearthed’s analysis had been tested between April 2016 and mid-2017, when there was no not-to-exceed limit in force for the RDE test. “All Groupe Renault vehicles are, and always have been, homologated in accordance with the laws and regulations for all the countries in which they are sold,” he said. “They all conform to the standards.”

He added: “Without waiting for the next standards (Euro 6D), Groupe Renault has defined a range of actions that have been applied gradually in the production of Diesel Euro 6b vehicles since mid-2016.”

These included widening the range of conditions under which Renault cars’ exhaust gas recirculation systems (one of the technologies used to reduce NOx emissions) are fully operational, and increasing the frequency and efficiency with which the cars’ NOx traps “purge” accumulated material.


Volvo’s real driving emissions test results feature a number of tests on diesel models fitted with a combination of Lean NOx Trap (LNT) and selective catalytic reduction technology (SCR) for reducing nitrogen oxide emissions, which recorded very low emissions on the road.

Models tested include 2l diesel versions of the Volvo XC40, XC60, and XC90. Overall average emissions in these tests ranged from 14mg/km (0.2 times the original Euro 6 limit of 80mg/km) up to 35mg/km (0.4 times Euro 6). Urban emissions ranged from 26mg/km (0.3 times Euro 6) up to 81mg/km (just 1mg/km over the original Euro 6 limit).

In all cases, emissions were less than half the maximum on road limit allowed under the current Euro 6d-Temp standard. A Volvo spokesman confirmed that these vehicles had been type-approved to Euro 6d-Temp.

However, Volvo also had some diesels approved during the monitoring period that were not fitted with SCR technology, and which produced higher NOx emissions in RDE testing.

The highest overall average emission level recorded was 304mg/km (3.8 times Euro 6) in a test on a V90CC. The highest urban emission level recorded was 332mg/km (4.2 times Euro 6) in a test on a Volvo S90.

The Volvo spokesman said that all Volvo diesel vehicle models “currently produced without SCR technology will be replaced by models with SCR technology before 1 September 2018”.

VW Group

The VW Group brands in Unearthed’s analysis – Audi, Skoda, Seat, and VW – were the only ones not to publish figures for their cars’ real driving emissions test performance in urban driving, or to provide those figures on request.

This makes a full comparison of these cars with those of other brands impossible, because the current RDE test requires cars to stay within the not-to-exceed limit both on average overall and in the urban section of the test drive.

Despite this, the overall average NOx emissions VW Group has published for the diesel cars it brought out during the monitoring period give some idea of how they would fare under current RDE limits.

VW Group has published summary results for tests on more than two dozen vehicles put through RDE testing during the monitoring period. Nine of these tests recorded average emissions above the 168mg/km limit that applies to all diesels approved since September 2017.

The highest emissions reported were for Audi’s 1.6l A3 and Q2 models, at 324.3mg/km (or 4.1 times Euro 6). These two models are part of the same “PEMs test family” (a collection of similar models that can be grouped together to limit the number of tests needed), but VW Group declined to say exactly which model was used in this test. Other tests on models in this family recorded emissions ranging from 259.1mg/km (3.2 times Euro 6) to 113mg/km (1.4 times Euro 6).

The next highest was Skoda’s 1.6l Karoq and Octavia models, at 269.5mg/km (or 3.4 times Euro 6). Likewise, these two models are part of the same PEMs test family.

Other models that exceeded the 168mg/km limit included the 1.6l Seat Ateca, the 2l Skoda Octavia, and the 2l VW Golf.

However, VW Group also brought out a number of SCR-fitted vehicles with overall average emissions below the original Euro 6 limit, of 80mg/km. The best performers included the 2l VW Arteon, with emissions ranging from 11.6mg/km (0.1 times Euro 6) to 30.7mg/km (0.4 times Euro 6). Likewise emissions for the 1.6l VW Tiguan were 15.7mg/km (0.2 times Euro 6) and for the 2l Tiguan were 30.7mg/km (0.4 times Euro 6). Tests on Skoda’s 2l Karoq and Kodiaq models also stayed below the Euro 6 limit for overall average emissions.

VW Group declined to comment.