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New diesels proven to be as clean as petrol models

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The latest diesel cars emit significantly less nitrogen oxide (NOx) than the upcoming Real Driving Emissions 2 (RDE2) regulations will require, according to new research.

Stringent testing by German automobile club ADAC shows that some diesel cars emit almost no NOx, during on-road testing – suggesting the latest models are as clean as their petrol counterparts.

In January 2020, tougher RDE2 rules will be introduced, requiring all new models launched to achieve 80mg/km or less (60mg/km for petrol). This will be a part of Euro 6d.

A conformity factor for the on-road test will be allowed, meaning the actual limit is 114mg/km for diesels and 86mg/km for petrols – significantly higher than any of the vehicles tested by ADAC.

A year later, in January 2021, all cars sold must achieve the more stringent figures. The conformity factor will be removed by 2023.

Current rules (RDE) require diesel cars to emit no more than 168mg/km of NOx, but the worst performing car tested by ADAC – the Honda Civic diesel – emitted just 101mg/km. (See below for full test results)

Following the WLTP re-homologation exercise that took place in 2018, the introduction of RDE2 will require all car makers to re-test their entire model ranges with an on-road test.

Nearly all the cars tested by ADAC emitted less than 50mg/km and the Mercedes C 220 d had no NOx emissions at all.

The Volkswagen Golf diesel performed exactly the same as the petrol version, emitting 14mg/km of NOx.

The best performing petrol car, a Suzuki Ignis 1.2, emitted 3mg/km.

ADAC performed the tests using a portable emissions measurement device (PEMS), in the same way as the official test.

Under the current company car tax rules, diesel vehicles that achieve RDE2 will not require the 4% diesel surcharge to be included in a drivers benefit-in-kind tax.

Currently, only the Mercedes A 220 d and B 200 d have been officially tested and approved under the regulations.

Jaguar has confirmed that the XF range will feature RDE2 approved engines by the end of the year.

Diesel car NOx emissions, as tested by ADAC:


RDE: NO x 
in mg / km

Audi A8 50 TDI


BMW 520d Steptronic 


BMW 520d Touring 


BMW X2 xDrive 20d 


Citroen Berlingo BlueHDI 130 


Honda Civic 1.6 i-DTEC 


Kia Ceed 1.6 CRDi


Mercedes A 180 d


Mercedes C 220 d


Opel Astra 1.6 D


Peugeot 308 SW BlueHDi 180


Volvo XC60 D5 AWD


VW Golf 1.6 TDI SCR



Petrol car NOx emissions, as tested by ADAC:


RDE: NO x 
in mg / km

BMW 218i Active Tourer


BMW 230i Coupe


Hyundai i20 1.0 T-GDI


Kia Ceed 1.4 T-GDI


Mercedes-Benz A 200 DCT


Renault Megane TCe140


Suzuki Ignis 1.2


Suzuki Swift 1.2 AWD


Suzuki Swift Sport 1.4


Volvo XC40 T5 AWD AT8


VW Golf 1.5 TSI


VW Golf 1.5 TSI BM DSG


VW up! GTI


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  • Edward Handley - 25/02/2019 11:27

    No surprises here - we have known for some time that diesel technology has improved in leaps and bounds and that most diesels are far cleaner than some people in the green lobby will admit. That of course does not deter the politicians from ranting about air quality and dirty diesels, particularly when setting up LEZs or ULEZs that do not ban all but the very latest diesels to prevent the air being polluted, they just charge them a fortune. Is the money used to improve air quality in some way? Dream on - its just a tax in environmental sheep's clothing.

  • Iain Ross - 25/02/2019 11:31

    If I'm reading this correctly - Although not officially tested the majority of current diesel engines fitted are RDE2 compliant. If when tested current diesel cars are proven to be within the RDE2 limit could a legal challenge be mounted to force HMRC to retrospectively refund the additional 4% diesel BIK charge?

  • Paul Gauntlett - 25/02/2019 16:37

    The article 'New diesels proven to be as clean as petrol models' proves the point that its old diesels we need to get off our roads not all diesels. As a long distance traveller I also use the train fairly frequently but the environmental credentials of that are sometimes let down but getting in a old minicab at the other end. Local licencing laws need to prevent diesels older than 5 years being used as Taxi's and the Government would do well to bring back more aggressive scrappage schemes which will hopefully also give the new vehicle market the boost it needs.

  • John - 25/02/2019 21:15

    Smoke and mirrors again - this is just about NOx emissions, what about the particulate emissions for diesels??

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