Independent, impartial advice for car buyers and car owners

Find an Expert Rating: 

What is the future of diesel cars in the UK?

Our Expert Partners

Motorway 600x300

Sell your car with Motorway
Find out more

Motors 600x300

Find your next car with Motors
Find out more

Leasing dot com 600x300

Car leasing offers from Leasing.com
Find out more

ALA Insurance logo 2022 600x300

Warranty and GAP from ALA Insurance
Find out more

MotorEasy logo 300x150

Warranty, servicing and tyres from MotorEasy
Find out more

Mycardirect subscriptions – 600x300

Carsubscriptions from Mycardirect
Find out more


The current ‘Dieselgate’ scandal involving Volkswagen cheating on a US emissions test has caused a great deal of controversy.  People at Volkswagen have fallen on their swords, the share value has plummeted and it still remains to be seen how badly the company’s sales will be affected in the coming months.

It has also opened other cans of worms when it comes to the whole issue of how cars are tested for fuel consumption and exhaust emissions, and whether diesel cars should be taxed/banned/scrapped (depending on which lobby group you choose to align with) because we are now convinced they are killing everybody.

The issues have all become blurred.  On the one hand, Volkswagen is in trouble for cheating on a test because they were unable to pass it legitimately; on the other hand, people are complaining that testing is too easy and does not reflect ‘real-world’ driving. Diesel cars are now cleaner than they have ever been, yet there are growing calls for them to be banned from built-up areas. So let’s try and look at each issue separately.

The Volkswagen ‘Dieselgate’ issue

The Volkswagen Dieselgate scandal concerns the company manipulating its engines to deactivate emissions equipment in normal driving circumstances, meaning the affected cars are producing much higher levels of pollution than they should be.

A huge amount has been written already about Volkswagen’s specific case. A lot of it has been complete rubbish, some of it has been good and plenty is still speculation because there is still a long way to go before it is all resolved.

It’s fair to say that the company has done a Bad Thing, and it is going to cost them dearly in terms of fines and other penalties, plus the costs of ‘fixing’ the cars in question, plus the inevitable loss of sales and company goodwill, plus the hit to the company’s share price that has already led to the announcement that all non-core projects will be cut. This will not only affect the Volkswagen brand, but the other brands they own or control – Audi, Bentley, Bugatti, Ducati, Lamborghini, MAN trucks & buses, Porsche, Scania trucks & buses, SEAT and Skoda.
Volkswagen VW diesel TDI BlueMotion EA189 scandal 5

And of course, that’s assuming that authorities around the world don’t uncover any further cheating from Volkswagen as they now go about re-testing a number of vehicles. Things could possibly get even worse for the German giant…

Diesel cars and air quality

Any vehicle powered by an internal combustion engine produces some form of pollution. Carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx) and various other nasties all come out of engines – they always have done and they always will do. Modern engines are much more efficient than older ones, so they produce fewer pollutants, but they still pollute. Different engines produce different types and quantities of these gases, and this is where science and politics took us down a path that has proved problematic.

With increasing concern at the impact of CO2 on our planet and its contribution to global climate change, governments around the world started to introduce tough new CO2 limits for car manufacturers. As a result of this focus on CO2 emissions, in conjunction with rising oil costs, car manufacturers started investing heavily in developing diesel engines.

Diesel engines generally use less fuel and produce less CO2 than petrol engines. This is a good thing for global CO2 levels and the driver’s wallet, but the catch is that diesel engines produce higher levels of toxins like NOx. And that has become a problem.

NOx is a big local pollutant, which has serious health implications for anyone exposed to high levels of it for prolonged periods. The massive increase in diesel vehicles in built-up urban centres has meant correspondingly large increases in NOx being inhaled by everybody, and scientists are now suggesting that this is having serious effects on our health. Hence there are growing calls for diesels to removed from urban centres, one way or another. Manufacturers and their representatives are terrified at this prospect, since they have invested billions of pounds in current and future diesel cars, and they stand to lose a lot if there is a move away from diesel cars.

CO2 is still a big global problem, but NOx is a big local problem. CO2 won’t kill you now, but NOx will. However, CO2 could kill all of us eventually. Chasing CO2 – and therefore pushing diesel engines – at the expense of everything else for the last decade was the wrong move, but a kneejerk change of policy could create even more problems in years ahead.

We need to balance the two. In an ideal world, diesel would be limited to motorway and A-road vehicles, and petrol would be limited to city driving. But we don’t live in an ideal world and we need solutions that are realistic.

Also, it is a ridiculous situation that buses, vans and taxis have been exempt from the tougher emissions laws applied to passenger cars over the last years. These make up a huge percentage of the vehicles on city streets each and every day, and they produce far more pollution than any Volkswagen…

A typical London black cab produces far higher levels of emissions than a passenger car

Testing cars for fuel consumption and emissions

All manufacturers use various methods to ‘optimise’ their cars’ performance in lab testing environments. These methods are perfectly legal, but they do distort the laboratory results compared to normal driving circumstances.

We have written previously about the variation between lab tests and ‘real-world’ conditions, and debate has now been ignited about how cars should be tested for emissions and fuel consumption. After years of building discontent, the Volkswagen Scandal has triggered a real push from various quarters to see the rules updated.

The idea that official fuel consumption and emissions testing should be done in the ‘real world’ sounds great in theory, but wouldn’t work at all. How can you compare Car A tested by Team B on Test Route C in the UK, with Car X tested by Team Y on Test Route Z in another country? The variations would be enormous. Lab testing allows us to eliminate the variables, so everyone is measuring the same thing in a comparable fashion. What we need is for the lab testing to be far tougher, so it is representative of the load that engines face in normal driving.

emissions test on a Volkswagen Golf TDI


EVs and alternative fuels will have to play a much bigger role if we want to keep reducing CO2 while also controlling NOx and other local pollutants. Ultimately, we need to reduce our reliance on fossil fuels (if we stopped buying oil from the Middle East and relied on our own reserves, there’d be far less violence in the Middle East for a start, but that’s another story…).

The future of the car will not be straight choice between petrol and diesel. We need to make sure both are being used in the most favourable circumstances, and push ahead with other energy sources like natural gas and biofuels. We will also see more vehicles where a petrol/diesel/natural gas/hydrogen engine is used to generate electricity for an electric motor to do the actual driving. Electric motors are far more efficient than combustion engines, and this is where the big future lies.Diesel car exhaust producing emissions

The latest from The Car Expert

Stuart Masson
Stuart Massonhttps://www.thecarexpert.co.uk/
Stuart is the Editorial Director of our suite of sites: The Car Expert, The Van Expert and The Truck Expert. Originally from Australia, Stuart has had a passion for cars and the automotive industry for over thirty years. He spent a decade in automotive retail, and now works tirelessly to help car buyers by providing independent and impartial advice.