If you have been perusing websites looking at new car deals recently, you can't have helped but notice the drive towards environmentally-friendly motoring. The number of hybrid and electrical options are expanding, while petrol-powered cars are becoming ever cleaner and more efficient.
But what about the diesel? Could it be a victim of the new green era?
The senior environment advisor to the Mayor of London Boris Johnson has told the government that owners of diesel cars should be taxed more to incentivise cleaner petrol and electric cars.
Matthew Pencharz told The Telegraph: "In the last 15 years we've seen dieselisation of the car fleet, switching from under ten per cent of the market to more than half, but diesel has exacerbated greatly the air quality problem in London."
Essentially, the current push to reward fuel-efficient cars via carbon dioxide-based VED tax has slightly backfired, as although diesels are frugal, they can be much 'dirtier' in terms of their exhaust emissions.
The subject of air quality is one that has been hotly discussed in the transport sector, with a study from Public Health England earlier this year showing that the risk of death from air pollution in central London was almost four times higher than in the cleanest areas of the UK. Furthermore, the European Commission began 2014 by launching legal proceedings against the UK for exceeding agreed air pollution limits. The problem with diesels is that they emit more smog-forming nitrogen dioxide and PM10 particulate matter.
As such, the London Mayor's office is putting pressure on the government to penalise diesels both old and new via the tax system.
"We want a tax weighting on diesels. Over time it would retrospective. We want to see bit less diesel and a bit more petrol," said Mr Pencharz.
And this would not just be an issue in London, with the advisor explaining the pollutants are a national problem and that air quality improvements would benefit everyone who lives in the UK. The next step in the process will see Mr Pencharz outline his plans at the Parliamentary inquiry on air quality due to take place later this summer.
Although cars and their emissions have been tightly governed by Europe-wide regulations that have got increasingly stringent over the years, authorities have so far failed to take the stop-start nature of city driving into account, resulting in Euro standards 4 and 5 failing to deliver the NOX reductions they targeted.
When Euro-6 standards roll out in September, new diesels will be subject to a further reduction in NOX emissions, but that may not be enough to stop the government from implementing a change in taxation, as the Mayor still wants more people to switch to petrol-electric hybrids or electric powered cars.
This news follows the announcement of plans for an ultra-low emission zone in London in 2020 that could ban older petrol and diesel cars.
It is understood that the view of the mayor's office is that as long as people are adequately informed of the proposals it would not be unreasonable to ban someone or tax them higher for a car they purchased relatively recently.