There are diesels that create up to 25 times more pollution than official testing shows? Surely, that’s a mistake?

We’ve written about clean diesels, false emissions, and wayward fuel economy figures in the past, and while diesel emissions are always a hot topic; it seems that not one week goes by without another nail being placed in the coffin of diesels, but the manufacturers really aren’t helping themselves.

A recent headline by Which? states that nearly 80% of modern, Euro 6 compliant diesels aren’t reaching anywhere near the 0.08g/Km emissions standard to be Euro 6 compliant one model, in particular, is 25 times over that limit. Is this just ‘click-bait’ or a genuine bit of foul play by car manufacturers?

Witch? hunt?

Which? have tested 61 new car models (all diesel) since the beginning of 2017, with the intention of seeing just how close they are to the Euro 6 rate for emissions, specifically Nitrogen Oxides (NOx). 77% of the cars tested failed to meet the 0.08g per kilometre standard, with the Subaru Forester 2.0d Sport Lineartronic coming in at 2.022g, but on average, the NOx levels were at 0.27g/Km.

However, it must be pointed out that the testing wasn’t Euro 6 compliant testing, in fact, a spokesperson for the Society of Motor Manufacturers and Traders (SMMT) said: “The non-official test employed by Which? is very different from the current EU testing, so it’s no surprise it delivers different results. Only the official tests accurately compare models on a like-for-like basis”.

The different test

Even under the new Worldwide Harmonised Light Vehicle Test Procedure (WLTP), testing is mainly done under laboratory conditions, giving the manufacturer the ability to ‘optimise’ their test vehicle(s) settings, this can include switching to an ‘eco’ mode, tyre inflation, low fuel loads (reduced weight) and a number of other considerations.

Whereas the Which? test runs the vehicles in the standard mode that they start up in (no eco setting), with 200kg of weight (roughly the equivalent of two occupants and a full tank of fuel), with all systems – air conditioning, lights and radio in use and they include a motorway phase.

Clearly, it would seem that some manufacturers can optimise their vehicles better than others, but there were also a number of vehicles that fell way below the Euro 6 standard, even under the more arduous testing conditions, so what (if anything) does the test mean?

Legally speaking, the car makers aren’t breaking any law – they’re doing exactly as they’re allowed to do under the test procedures, this isn’t a ‘Dieselgate’ scandal, merely … an exercise in understanding and applying rules.


Targeting the consumer angle is a moot point – the WLTP tests (as the SMMT point out) are comparing like-for-like, which means the end result is a direct and truthful comparison between models or brands, so as long as you know that Car A has fewer emissions than Car B, you’re in possession of the relevant facts and figures.

Yes, understanding that in the real world, under strenuous conditions, Car A doesn’t actually get near the advertised figure is all well and good, but let’s be honest, if emissions and pollution levels drive your desire, you won’t be looking to buy a diesel, regardless of what the manufacturer claims.

The best and the worst

The top 5 dirtiest diesels:

  1. Subaru Forester 2.0d Sport Lineartronic – 2.022g/km
  2. Renault Grand Scenic Energy dCI 160 Bose Edition EDC – 0.896g/km
  3. Renault Captur dCI 90 Intens – 0.725g/km
  4. Peugeot 5008 BlueHDi 150 Allure – 0.700g/km
  5. Ford Kuga 2.0 TDCi S/S Vignale 4×4 – 0.655g/km

And the top five cleanest:

  1. BMW 2 Series 218d Active Tourer Steptronic – 0.014g/km
  2. Mercedes-Benz E220d 9G-Tronic – 0.024g/km
  3. Mercedes-Benz E220d 9G-Tronic Estate – 0.028g/km
  4. BMW X2 xDrive 20d M Sport X Steptronic – 0.031g/km
  5. Vauxhall Grandland X 2.0 Innovation Automoatic – 0.034g/km

Testing times

The WLTP testing has been in force (for new car types) since September 2017, with all new registrations being compliant by September 2018, but as we’ve pointed out, it will really only be useful for a comparison against different models or brands – not as a benchmark of what you can expect (especially in terms of MPG).

If you’re specifically looking to purchase a new vehicle, and it has to be diesel, then the figures will be relatable and perhaps a better indication than previous testing processes – the New European Driving Cycle (NEDC) was introduced back in the eighties, and as such, it left a little to be desired as technology marched on, despite some flaws, the WLTP has to be better (and more accurate) than the NEDC, but whatever the process or procedure, there will always be an organisation willing to decry it as unrealistic.

Do you think better emissions tests should be introduced to reflect real-world driving? Is it a good thing that diesel will be banned from sale in 2040? Let us know below

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