Amid headlines of manufacturers cheating emission tests and the harmful effects of NOx on our health, is there any room left for a defence of diesel?
Diesels are distinctly out of fashion. With consumer confidence in them shot after various emissions scandals, higher UK road taxes, new MOT rules and some cities around the world banning them outright, driving a diesel seems to be becoming taboo.
Add to this growing public awareness of the effects of NOx emissions and the subsequent plummeting sales, and it seems it may be curtains for diesels.
Decline and fall
Since VW’s ‘Dieselgate’ rocked the world in 2015, sales of diesel cars have plummeted in the UK, falling from 50.1% of overall new car sales in 2014 to just 31.9% as of July, according to data published by the SMMT (Society of Motoring Manufacturers and Traders).
And it’s not without reason. Public awareness about NOx (oxides of nitrogen) emissions from diesels – linked to tens of thousands of premature deaths around the world – has grown massively.
Air pollution from vehicle emissions is a very real problem. In 2017, for example, it took just five days for Brixton Road in London to break its NO2 (nitrogen dioxide) limit for the entire year.
And the results from our new research paints a fairly dirty picture for diesel: on average, the 61 diesel cars we tested produced 0.27g/km of NOx – nearly three and a half times the official Euro 6 limit (0.08g/km).
Diesel defence
But does it have to be this way? Diesels generally produce less carbon dioxide (CO2) and carbon monoxide (CO) than equivalent petrol cars.
And they don’t inherently have to be NOx-spewing monsters. Some manufacturers are starting to produce some squeaky clean diesel cars.
Currently they are the exception rather than the rule, but we’ve found two Mercedes and one BMW diesel car that produce less or the same NOx emissions as your average petrol.
AdBlue & SCR make a difference
More and more diesel cars are using Selective Catalytic Reduction (SCR). It’s an active emissions system that injects urea, most commonly AdBlue, into the exhaust system to cancel out harmful emissions.
And it makes difference. We found that diesel cars with an SCR system, on average, produced about a third of the NOx than cars without one.
So fitting these systems on all diesels could make a huge difference to NOx emissions.
But it’s really a question of whether manufacturers think it’s worth the cost to add these sophisticated systems to their entire range of diesel cars – something that will no doubt be influenced by the tough new on-road emission tests that will be in force for all new cars by September 2019, known as RDE step 1, and will require better real-life emission control than before.
Room for reform?
Some manufacturers clearly do think there’s public appetite for cleaner diesels, a Mercedes spokesperson telling us previously:
‘Our new engines are both highly efficient and produce low levels of NOx. It’s a fact that it’s worth improving the modern diesel instead of banning it.’
That’s one opinion, but it is true that relatively ‘clean’ diesel cars are possible – and available, if you’re willing to pay for them.
The problem is these ‘clean’ examples really are the exception and, it seems, time may already have been called on diesel generally.
But what do you think? Do you agree that diesel has a future if it can be improved? Is the public snubbing of diesel going too far?
What about if someone presented you with a clean diesel car – it produces less NOx, CO2 and CO, and costs the same as an equivalent petrol car – would you buy it or not?
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