In 2014, the VW diesel emissions scandal unravelled across the world's media. The story pointed the spotlight at diesel cars and their environmental impact. For the first time in nearly a decade, the trend of ever-increasing diesel car sales went into reverse.
So what is it about diesel engines and are they really worse for the environment than petrol equivalents?
From 2001, the labour government pushed diesel as the economical and environmental engine choice. Significant tax breaks were offered to business drivers and fleets as well as incentives for manufacturers. Nearly a decade later, evidence that diesel could be more damaging to the environment than petrol counterparts started to emerge.
Diesel, in almost all cases, delivers better fuel economy than petrol, and unfortunately, an assumption is often made that economy and emissions are the same thing. Fuel economy is the amount of fuel burned to cover a given distance, whilst emissions are the volume of particulates produced in a given distance. If a car travels 100 miles and uses 4 gallons of fuel, it could generate more emissions than a more economical one traveling the same distance. This is where diesel falls down. Research for Transport for London in 2017 concluded that a 1.4 litre VW Polo diesel emits as much nitrogen dioxide as a fully loaded lorry.
In the vast majority of cases, diesel cars produce less CO2 than petrol cars; however, they produce more toxic emissions as a whole per mile driven than a petrol equivalent, even when considering their greater efficiency. Perhaps more concerning is that the type of emission generated in the greatest volume by older diesel engines is nitrogen oxide (NOx) which is linked to respiratory conditions such as asthma.
The negative impact diesel engines can have is particularly hard felt in cities where large volumes of stop-start traffic create a real health hazard. In February, transport secretary Chris Grayling suggested that drivers should think long and hard before buying a diesel car. His intervention follows reports that the government is considering a scrappage scheme for pre-EU4 diesel cars to improve air quality.
So, are diesel cars an endangered species?
The 2001 decision made by labour highlights the potential dangers of misinformation. Conversely, however, it shows that politicians can effect significant change in purchase behaviour.
The framing of the EV debate currently exhibits certain similarities. Where (and how) is power being generated? Is there enough capacity in the national grid to fulfil demand?
What is done with damaged or out of date battery cells? These questions have not been satisfactorily answered yet, but the groundwork is being laid. What is becoming clear is that unless significant reductions in emissions can be achieved, diesel car sales will likely fall irrevocably in coming years. In particular, small capacity diesel is almost certainly dead. Volkswagen recently announced that they were shelving their next generation 1.5 litre diesel because the cost of making the engine comply with emissions tests made the business case untenable.
Alternatives such as electric, hybrid and petrol, which are receiving significant investment from manufacturers, look likely to fill the gap. This should be positive from an environmental perspective, but change is never cheap. Motorists will be paying a price in the form of reduced economy in the case of petrol alternatives. (The impact of the new “real world” economy tests being introduced this September will mean that new cars will appear – on the surface at least – to be less economical than older models. The other whammy is cost. Initial purchase price in the case of electric and hybrid vehicles is higher and we wouldn’t bank on Government grants of up to £5,000 being around forever to help soften that blow…
The outlook is less certain for heavy goods vehicles. Larger diesel engines are much better suited for transport needs and the new Euro 6 standard, though costly, is a significant step forward. The industry is heavily invested in diesel powertrains with most manufacturers not offering any viable alternative. In spite of the spotlight on emissions, it could be some time before we see alternative powertrains in commercial vehicles.
Manufacturers need to get to a place where power trains are fit for purpose, and this likely won't take long. EVs for example are superbly suited for city driving, but are a bad fit for long-distance purposes. Conversely, diesel is well-suited for long journeys, but is not a good fit for city journeys.
For now, and in the near future, we need to focus on ensuring that marketing communications and strategies are as sophisticated as the vehicles that are the subject matter of those ads. In particular, we need to educate customers on the benefits and drawbacks of certain configurations. By providing consumers with accurate information, we arm them with the tools to make an informed decision as to the right vehicle to fit their needs.