Business Personal Finance

Monday 18 November 2019

Are diesel cars running out of fuel?

Motorists have turned to diesel in the belief that it's more eco-friendly. But is the tide turning again? John Cradden reports

In a market where the petrol engine had held sway for so long, it took less than 10 years for Irish motorists to switch overwhelmingly to diesel-engined cars.

But while diesel now accounts for nearly three-quarters of all new cars sold today, the tide might well turn back in favour of petrol and other powerplants over the next decade because of growing environmental and reliability concerns.

London and Paris have recently focused attention on the link between the number of diesel-engined vehicles in cities and deteriorating air quality. London Mayor Boris Johnson, last year, proposed a scheme that would pay diesel car owners up to £2,000 to scrap their vehicle in favour of a cleaner model, while the French capital recently voted through measures to ban all diesel vehicles from the city centre by 2020.

Although the burning of diesel emits lower C02 emissions than petrol, it also results in higher air pollution because it emits dirty soot particulates that are known to cause respiratory problems. It also produces nitrogen oxide (NOX) emissions that are linked to respiratory issues in children and other vulnerable groups.

Shane O'Donoghue
Shane O'Donoghue

However, at the same time, car makers say they have been forced by ever-stricter EU emissions legislation over the years - most recently by the latest 'Euro-6' standards - to develop more sophisticated technology to lower soot and NOX emissions from their diesel engines, including the use of diesel particulate filters (DPFs).

But this, in turn, may have led to growing complaints over the servicing and repair costs of modern diesel cars because of their greater complexity compared with petrol equivalents, not to mention that they are becoming more expensive to buy and maintain.

So, has diesel had its day? Or has the Irish motorist been over-sold diesel cars? Should consumers think twice before buying a diesel car now or in the future?

Shane O'Donoghue, a motoring journalist and editor of, says he gets loads of queries all the time about the merits of diesel versus petrol, but they all focus on trying to figure out which would be cheaper in terms of the total lifetime cost of ownership. None of them, he said, have specifically mentioned concerns about NOX or soot emissions - only C02.

"In fairness, diesel cars are within EU law in terms of NOx so the car makers have done nothing wrong," he said. "I would suspect that, despite the situation in London and Paris, few drivers in Ireland are aware of the ins and outs of it all."

Some readers, however, have spoken of how shockingly unreliable and costly modern diesel cars have been to run, with many experiencing huge repair bills for replacing items like DPFs.

DPF failure is a common but expensive problem on modern diesels, mainly because, in order to work efficiently, a car so equipped needs to get on the motorway or up to a decent speed every so often so that the engine's exhaust after-treatment system gets fully up to temperature. If it doesn't, the DPF can get clogged up.

O'Donoghue himself has fallen victim to an expensive DPF failure with his family's current car, a Volvo V50, because it was used primarily for short journeys.

It is now used by his wife for a long-ish daily commute, but with a change in her job next year and a return to a much shorter commute, they are considering ditching the diesel in favour of a low-emissions petrol car.

All the same, he disagrees that we have been over-sold on diesel.

"Sure, the taxation favours them [diesels] as they inherently have lower CO2 emissions," says O'Donoghue, "but that way of thinking has lead the car makers to produce petrol cars with much lower emissions too, and right now there are genuinely good options from both."

In Britain, the industry representative body, the Society of Motor Manufacturers and Traders, launched a campaign to highlight the strictness of the new Euro 6 regulations and to "challenge the increasing demonisation of diesel" vehicles.

The Europe-wide law, which will come into force in September, limits nitrogen oxide (NOx) emissions from new diesel cars to 80mg/km in order to bring down air pollution levels that breach health regulations in many EU cities.

Here, the Society of the Motor Industry (SIMI) doesn't seem as concerned about any "demonisation of diesel", but chief executive Alan Nolan concedes that diesel is likely to fade in popularity as consumers see that the latest generation of petrol engines have much improved in terms of C02 emissions, but also that diesel cars have their own disadvantages.

"From a cost benefit point of view, a petrol car may make more sense for them because diesel cars will be very low on C02 and very low on fuel consumption but they do require higher maintenance. They are much more sensitive to neglect."

Neither the Department of Transport nor Dublin City Council has publicly commented on the air pollution issue, but Nolan doesn't anticipate moves here to specifically penalise users of older diesel cars in ways proposed by London and Paris.

It would be wrong to incentivise one type of fuel over another in a bid to reduce air pollution, he said, citing the example of the hype not so long ago about the potential for biofuels as an eco-fuel of the future, until it became clear that it was not the way forward because of likelihood of a lop-sided impact on agricultural production and the Third World.

"You can't oscillate between one fuel and another. You do have to cast the net as widely as you can."

Irish Independent

Also in Business