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If you’re considering buying a new or used diesel-engined car then you could be forgiven for thinking that you’ll be ostracised by all right-thinking people for such a reckless anti-environmental choice.

You might also be a little confused over the government’s stance on diesel; having encouraged its usage for many years for its fuel efficiency and low carbon dioxide (CO2) emissions, it performed a dramatic U-turn in the 2017 Autumn Budget by raising its benefit-in-kind taxation for company car drivers and increasing the Vehicle Excise Duty (VED), or road tax, charge.

On top of this, there’s been plenty of misinformation trotted out in some quarters of the popular media about diesel that has tarred the latest generation of more efficient and cleaner diesel engines with the same brush as older and less refined units.

As a car buyer, you will want to choose the best fuel type for your personal requirements as well as the environment. And with this in mind, The Car Expert has dug deep into the diesel debate to assess the pros and cons of the fuel to help you with your car purchase decision making.

Why has diesel been demonised?

Diesel’s bad press can be traced back to 2015 with Dieselgate, when it emerged that millions of diesel-engined vehicles sold by Volkswagen Group brands were equipped with software programmed to give false nitrogen oxide (NOx) readings when subjected to emission tests.

The scale of the scandal cannot be overstated as it resulted in around 11 million vehicles being recalled around the world for rectification work across VW’s car and van brands, as well as Audi, Skoda and SEAT.

The whiff of the scandal has been present ever since, with the popular view that diesel engines are worse polluters than their petrol counterparts. To set the record straight, diesel engines produce lower carbon dioxide (CO2) levels than comparably-sized petrol engines but higher NOx, or particulate/soot, emissions.

However, the latest generation Euro-6 engines, which have been available on new cars since September 2015 have delivered significantly reduced levels of both CO2 and NOx – diesel has cleaned up its act.

What is the government’s stance on diesel?

The Autumn Budget clarified the government’s position on diesel; it doesn’t like the fuel and is now actively legislating against its usage. However, don’t panic! The changes were small and could have been much, much worse.

While the rights and wrongs of the government’s approach, after years of encouraging drivers to buy diesel-engined cars, can be argued at length, what is certain is that it will not allow itself to be seen to promote the use of the fuel by choosing to legislate against it.

From 6 April 2018, all company car drivers running diesels will see the long-standing 3% benefit-in-kind supplement raised to 4%; a move that will penalise individuals for choosing diesel for its fuel efficiency and therefore make it less attractive amongst some user-choosers; even though for high mileage drivers it is the only option.

An even more overt message was the penalising of new generation Euro-6 engines which were rounded on for not complying with the Real Driving Emissions Step 2 (RDE2) standards, even though they don’t currently exist and will not be mandatory on new cars until 2021.

This was a particularly bizarre move, worthy of Kafka, but by moving all diesels that do not comply with RDE2 (and that is currently all diesels) into a higher VED band from April 2018, the government has made a statement of intent; it might only equate to an extra £20 in the first year of registration but can be seen as an indicator of how diesel will be treated in the future.

Further down the line, the government has pledged to outlaw the sale of all new purely diesel or petrol cars from 2040.

Are all diesels penalised by new urban clean zone charges?

No. Some UK cities are looking at ways of improving air quality in the major conurbations and are considering the introduction of a toxin charge on older vehicles. London is currently leading the way with the £10 daily T-charge, which is paid in addition to the Congestion Charge.

The London scheme was introduced in October 2017 for diesel and petrol-engined vehicles powered by pre-Euro-4 engines, so that’s all cars registered before January 2005. Additionally, there have been reports that Mayor Sadiq Khan is considering a £12.50 daily levy on all diesels entering Greater London from 2019; a move that would penalise hundreds of thousands of families who have bought diesel-engined cars in good faith.

Will the resale value of diesel be impacted by the negative publicity?

This is the million dollar question and clearly an important consideration if you’re about to commit to a new or used car purchase.

What we do know is that new diesel sales are significantly down year-on-year, but there’s no shortage of used models coming into the market following several successive years of market growth.

The advance intelligence from Auto Trader, the UK’s biggest marketplace for used car sales, is that advertised prices are holding up. Despite average values falling £143 month-on-month in November 2017, year-on-year used prices were up 3% according to its Retail Price Index.

Diesel also remains the most searched-for fuel type amongst new and used car buyers, accounting for 55% of all searches on the Auto Trader website in November 2017.

Commenting on the findings, Karolina Edwards-Smajda, Auto Trader’s retailer and consumer product director, said: “The negative rhetoric surrounding diesel, which has been fuelled by the government’s recent announcements, is undoubtedly contributing to the decline in new and used car sales and has impacted used car prices in November.

“Although used diesels have been showing much greater resilience, with their value continuing to increase year-on-year, as well as remaining the most searched-for fuel type on our marketplace, our Retail Price Index does show a small month-on-month decline for the first time in eight months. It’s too early to tell whether this is an emerging trend or not, so we will continue to monitor prices closely.”

What are the alternatives to diesel?

Before considering the alternatives you need to weigh up exactly what you need the car for. The absolute prerequisite for choosing diesel is if you expect to do annual mileages of at least 10,000 miles.

Diesels are unsuited for short hop work because they need long distances to return anything near their claimed combined consumption figures and also to generate sufficient energy to burn off soot in their diesel particulate filters (DPF). A common cause of diesel car failures is blockages to their DPFs, requiring costly repair work.

Petrol is the most obvious alternative to diesel, with carmakers now delivering some outstanding downsized engines offering lower emissions, more horsepower and diesel-rivalling fuel economy.

Electric plug-ins are only suited to relatively short hop usage and require somewhere at home where you can easily recharge overnight. Recent years have seen improvements in ranges with the Nissan Leaf achieving a claimed 235 miles and the Renault Zoe 250 miles. However, these are optimal figures achieved in laboratory conditions. Real world stop-start driving can severely reduce these ranges especially once the heating or air-conditioning are switched on.

The best compromises are any number of petrol or diesel hybrids, from the Toyota Prius to the Mercedes-Benz C 300h, which remove the issue of range anxiety and deliver some outstanding fuel economy. It’s also worth looking at plug-in hybrids (PHEV) such as the Mitsubishi Outlander or Kia Optima, which are low-emission hybrids boosted with batteries that can be recharged from the mains to deliver pure electric power.

So, should I still consider buying a diesel car?

If it’s a new car and your annual mileage covers a lot of long journeys, then yes. It will be fitted with the latest Euro-6 type engine and will be high on fuel economy and low on emissions. If you are buying used then factor in that models registered before September 2015 may have older generation Euro-5 engines which, at some stage in the future, are likely to be the next to be scrutinised by the government and local authorities.

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Curtis Hutchinson
Curtis Hutchinson
Curtis Hutchinson is a member of the Guild of Motoring Writers and has been a senior motoring journalist for over 25 years. He has written extensively about the automotive industry as editor of both Company Car and Motor Trader where he won the coveted Newspress Business Publication of the Year Award. His work also appears in Fleet World and Fleet World International. In 2016 he was part of the founding team behind the relaunched London Motor Show.