Dirty diesels: most polluting cars revealedDiesel emissions testing carried out by Which? has revealed the worst diesel cars for air pollution. The figures highlight a huge variation across the industry, with the worst offenders emitting up to nine times the level of dangerous pollutants permitted in official tests. Read on to discover more about the dirtiest diesels and how Which? conducted the tests.

There are emission laws in place to limit the amount of NOx produced by cars, but Which? has uncovered huge differences in the amount of NOx emissions produced by diesel cars from different brands. Crucially, Which? uses real-world tests, replicating the way drivers really drive their cars.

Which? has provided the averages for diesel cars tested between 2012 and 2016, with the results based on data for Euro 5 compliant cars, rather than the stricter Euro 6 emission limit. The results are presented in reverse order, with Euro 6 information included where applicable.

21. Mitsubishi: 0.31 NOx g/kmDirty diesels: most polluting cars revealed

The Euro 5 diesel limit is 0.18g/km of NOx, which means even the cleanest car on the list fails to meet the target. The Which? data is more accurate as the tests use more realistic cycles, including motorway testing, where the car is accelerated to and then sustains motorway speeds.

20. SEAT: 0.32 NOx g/kmDirty diesels: most polluting cars revealed

Of the figures, Richard Headland, Which? magazine editor, said: “While our tests show that some car manufacturers are making progress on reducing the amount of toxic emissions from their models, many have a long way to go in cleaning up their act.”

SEAT, Euro 6: 0.11 NOx g/km.

19. Audi: 0.33 NOx g/kmDirty diesels: most polluting cars revealed

Headland continued: “We hope that the improved official tests brought in later this year will more clearly name and shame those manufacturers that are failing to meet their obligation to lower emissions.”

Audi, Euro 6: 0.15 NOx g/km.

18. Skoda: 0.33 NOx g/kmDirty diesels: most polluting cars revealed

The improvements mentioned by Richard Headland refer to the World Harmonised Light Vehicle Test Procedure (WLTP), which replaces the much-criticised New European Drive Cycle (NEDC). In a nutshell, WLTP will introduce stricter controls and cycles to reflect normal driving behaviour.

Skoda, Euro 6: 0.14 NOx g/km.

17. Volkswagen: 0.34 NOx g/kmDirty diesels: most polluting cars revealed

Perhaps unsurprisingly, the NOx figures for SEAT, Audi, Skoda and Volkswagen are within 0.2g/km of each other. As Which? points out, the Euro 5 diesel cars tested are part of the ongoing VW emissions investigation, so a question mark remains over the results.

Volkswagen, Euro 6: 0.11 NOx g/km.

16. Volvo: 0.40 NOx g/kmDirty diesels: most polluting cars revealed

Which? says it recorded a (comparatively) low NOx average across the seven Euro 5 Volvos it tested, but the four Euro 6 Volvo cars actually emit more NOx than the Euro 5 vehicles.

Volvo, Euro 6: 0.43 NOx g/km.

15. Toyota 0.40 NOx g/kmDirty diesels: most polluting cars revealed

Toyota performed well, with the Euro 6 figure even lower at 0.13g/km. However, this is still higher than the 0.08g/km European limit for Euro 6 vehicles.

Toyota, Euro 6: 0.13 NOx g/km.

14. BMW: 0.41 NOx g/kmDirty diesels: most polluting cars revealed

Which? is quick to praise BMW and MINI, saying that the 33 cars tested produced some of the lowest NOx averages for diesel cars. While MINI doesn’t feature in the Euro 5 results, it did produce the best result for Euro 6 compliant cars. A figure of 0.08g/km means it just meets the European target.

BMW, Euro 6: 0.14 NOx g/km.

13. Honda: 0.45 NOx g/mDirty diesels: most polluting cars revealed

To produce the figures, Which? analysed 278 diesel cars from leading manufacturers between 2012 and 2016. Five Honda vehicles were tested, producing a result of 0.45 NOx g/km.

12. Vauxhall: 0.46 NOx g/kmDirty diesels: most polluting cars revealed

Other brands for which only Euro 6 compliant cars are tested include Dacia (0.59g/km), DS Automobiles (0.26g/km), Mazda (0.21g/km) and Jaguar (0.18g/km). Meanwhile, in the Euro 5 table, Vauxhall achieves a figure of 0.46g/km.

Vauxhall, Euro 6: 0.25 NOx g/km.

 

11. Fiat 0.48 NOx g/kmDirty diesels: most polluting cars revealed

Meanwhile, four Fiats were tested, with a result of 0.48 NOx g/km.

10. Mercedes-Benz: 0.48 NOx g/kmDirty diesels: most polluting cars revealed

A total of 17 Mercedes-Benz cars were tested (7 Euro 5 and 17 Euro 6), with a Euro 5 result of 0.48g/km.

Mercedes-Benz, Euro 6: 0.15 NOx g/km.

9. Peugeot: 0.52 NOx g/kmDirty diesels: most polluting cars revealed

Peugeot finishes 9th in the Euro 5 table, making it the best performing French brand on the list. Its Euro 6 performance is one of the best recorded by Which?.

Peugeot, Euro 6: 0.11 NOx g/km.

8. Kia: 0.53 NOx g/kmDirty diesels: most polluting cars revealed

Kia finishes eighth, with a NOx figure of 0.53g/km.

Kia, Euro 6: 0.29 NOx g/km.

7. Citroen: 0.56 NOx g/kmDirty diesels: most polluting cars revealed

Slightly behind Kia we find Citroen, with a NOx figure of 0.56g/km.

Citroen, Euro 6: NOx 0.16g/km.

6. Ford: 0.58 NOx g/kmDirty diesels: most polluting cars revealed

There’s not a huge amount of difference between Ford’s Euro 5 and Euro 6 figure, with the more lax Euro 5 test revealing an output of 0.58g/km.

Ford, Euro 6: 0.49 NOx g/km.

5. Hyundai: 0.60 NOx g/kmDirty diesels: most polluting cars revealed

Hyundai is committed to delivering 14 or more new environmentally-focused models by 2020, which should go some way to improving this top five finish.

Hyundai, Euro 6: 0.40 NOx g/km.

4. Renault: 0.73 NOx g/kmDirty diesels: most polluting cars revealed

NOx emissions from the 16 Renault diesel cars tested are seven times higher than the Euro 6 MINIs tested. In response, Renault said: “Since mid-2015, Groupe Renault has committed to improve the performance of its anti-pollution systems. The vehicles tested by Which? would not have benefitted from this improvement plan”.

Renault, Euro 6: 0.72 NOx g/km.

3. Land Rover: 0.78 NOx g/kmDirty diesels: most polluting cars revealed

In third place is Land Rover, which was one of six manufacturers for which the consumer group only has average figures for Euro 5 compliant cars.

2. Nissan: 0.81 NOx g/kmDirty diesels: most polluting cars revealed

In response to the results, Nissan said: “We are committed to upholding the law and meeting regulations in every market where we operate. Specifically in Europe, all our vehicles sold in Europe meet the Euro 5/6 emission standards. This report, which looks at the variation between lab and ‘real world’ conditions, shows significant variances for most brands tested”.

1. Jeep: 1.74 NOx g/kmDirty diesels: most polluting cars revealed

That leaves Jeep to secure the unwanted position at the top of the dirty diesels tree. Jeep failed to provide a response to the research.