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Insight: Is it time to give up on the diesel engine, Autocar

Insight: Is it time to give up on the diesel engine?

What should we do about diesels?

Should we proceed buying them fresh in large numbers as we have done over the past thirty years? Should we defend them, spurn them, ban them from big cities or liquidate them from the road altogether? Is their proven low CO2 output vital in our fight to reduce greenhouse gases, or are their particulates and nitrogen oxides (NOx) so harmful – as an enhancing bod of research seems to display – that they should be eliminated from sale altogether?

Finding the correct answers to these searing questions seems to be clouding more and more car purchase decisions. There are supporters for each of the above courses of act – but the arguments for banning diesels are becoming ever more shrill, led notably by Sunday newspapers, that quote both doctors’ organisations and academic sources in support of their case, and diesel sales are falling as a result.

Yet precious little guidance through the diesel minefield is forthcoming, either from government agencies or the car industry. The only certainties for diesel-owning motorists – toughly 40% of the thirty million or so owners in the UK – is that they bought their cars in good faith and that tomorrow, come what may, they’ll need to get to their kids to school and themselves to work, mostly by car.

The industry’s view is multi-faceted and sophisticated. Very first, while cautiously admitting ‘more can always be done’, its experts believe that when current, rough Euro six (EU6) emissions standards are combined with much more realistic and impartial test regimes that arrive this September (called WLTP or Worldwide harmonised Light vehicles Test Procedure), a modern car’s output of NOx will have been cut to lil’ proportions. Diesels should be free to get right on with their job of contributing to lower CO2.

The latest figures from the SMMT, the UK’s car manufacturers’ club, indicate that CO2 emissions have been diminished for the past nineteen straight years and are now well over 30% lower (at an average for a fresh car of around 120g/km) than in 2000.

2nd, the automotive industry is understandably reluctant to criticise the cars it has already put on the road, on the grounds that they complied with the legislation of the time. UK car users have bought toughly a million diesels a year and there are an estimated 12m diesel cars and vans already on our roads. Penalising them would create havoc. Entirely switching the car parc, if you embarked now, could take twenty years.

Third, Europe’s motor industry needs to preserve its markets, viability and infrastructure to fund fresh, electrified cars planned along its ‘glidepath’ towards the 95g/km manufacturer fleet average required by two thousand twenty – and onward towards a hoped-for zero-emissions future in 2050. (In the UK, Jaguar Land Rover has just opened a fresh diesel plant in Wolverhampton and Ford builds most of its world requirement for diesels in Dunton).

Fourth, its bosses are utterly reluctant to wade into a elaborate, illogical debate that has conflated Volkswagen’s very publicised diesel emissions scandal in the US with a 15-year-old progression of EU emissions standards – presently at EU6 – whose fuel consumption results bear so little resemblance to owners’ practice that they are presumed to be dishonest. ‘They’re all at it’ is the common accusation.

The testing regime (called NEDC or Fresh European Driving Cycle) fastened to that 15-year progression is more at fault than the actual emissions standards. The forthcoming WLTP will switch all that and is welcome. The WLTP standards will be accompanied by fresh real-world driving tests, called RDE, and it is the combination of the two that will produce fresh, believable fuel consumption and emissions figures.

The government, meantime, is hamstrung (and embarrassed) by its promotion over past decades of a legislative framework that has appeared to encourage diesel adoption as a way of lowering CO2 – evidently at the expense of cutting NOx. Skill of the harmful effects of NOx (about a quarter of which emanate from transport across the UK, but about half in London) has enlargened greatly in the past five years, albeit government agencies have lately been made unpleasantly aware of university studies that embarked issuing NOx health warnings twenty years ago.

Officialdom is very reluctant to offend car users in large numbers, such as by outlawing or cost-loading diesel cars they bought in good faith. Lobbyists say offending the motorist has in the past proven to be about the most vote-sapping activity a government can take. Even London’s mayor, Sadiq Khan, who has loudly voiced a determination to improve London’s air quality by charging diesels £10 to penetrate the London congestion zone from October, is applying the charge to only pre-EU4 diesels, made before 2005.

“When EU4 was introduced for 2005, the industry’s attention turned to diesel particulates,” says Mike Hawes, CEO of the SMMT. “By the time EU5 arrived in 2010, they were the big issue. NOx wasn’t seen as bruising the way it is now, but I’m undoubtedly not telling the industry disputes the effects of NOx on human health: we’re no experts. Our concern shows in the speed we’ve brought anti-NOx after-treatments to market.”

What about diesel particulates? Consisting mainly of the ash left over from combustion, these are acknowledged as an significant problem and bruising to human health, but the automotive industry believes it has already moved to cut them dramatically by fitting cars with particulate traps from two thousand ten when EU5 was introduced.

Why isn’t there such concern over the pollution contribution of petrol cars? Because experts say that can be more lightly managed by increasingly effective catalytic converters, very first seen in the early 1990s. Levels of petrol harass pollutants rise less rapidly than diesels with extra speed, extra flow, difficult gradients and hard driving (which is why diesels have attracted all of those headlines about reputable cars producing ten times their advertised output of pollutants in real-world tests).

The lower compression ratios of petrol engines have traditionally resulted in their production of considerably less NOx than diesels from combustion. Neither in the past have they had the diesel’s harass ash problem, requiring a particulate filter. But the situation could be about to switch. The rise of more frugal, harder-working, smaller-capacity turbocharged petrol engines – with higher resultant compression ratios – is likely to mean they will also make more NOx. There are also strong indications that they may produce finer particulates that may be harmful and may need filters of their own. Research continues…

The most urgent problem, identified by London mayor Khan, shows up to be the profusion of oldschool diesels – notably well-worn and decades-old taxis, trucks and delivery vans as well as passenger cars – on our roads. The mayor has already hit the headlines, and been rebuffed by the government, for proposing a £500m scrappage scheme that pays diesel owners up to £3500 for ditching old diesel cars.

Before he left office, London’s previous mayor, Boris Johnson, also proposed a two thousand twenty clean air directive that would penalise pre-EU6 (2014) diesels and pre-EU4 (2005) petrol cars by charging their drivers £12 on top of the regular daily congestion charge to penetrate London’s congestion zone. Latest indications are that Khan’s administration will keep the idea but bring it forward by a year. The writing seems to be on the wall for old diesels. Those who need older cars for inward London will do better possessing petrol models.

What should the worried private car proprietor do about diesel ownership? Very first, say the experts, consider the kind of driving you do. If you have a healthy early diesel and never drive in urban areas, it’s no crime to keep it. You won’t be contributing to urban pollution, the urgent problem.

Steve Gill, director of powertrain engineering at Ford of Europe, says: “Our concern is that customers will stir away from diesels as a result of unbalanced coverage of the emissions situation. We’re not attempting to force diesels on customers – they should buy what they want – but we’ve had to reposition some of our products and we’re having discussions now about where to put our money in the future.”

In Autocar’s opinion, diesel car ownership must not be off the agenda, because a bedrock of diesel sales is necessary to keep CO2 levels falling, the latest cars are clean and the industry needs the sales to fund the electrification that is coming. There is no doubt that the cleanest cars, with both their particulate and NOx outputs ‘trapped’, are EU6 models produced from 2014. We’d choose one of those.

Were we about to buy a fresh diesel car, we’d consider delaying the purchase until models tested under the fresh, real-world WLTP process inject the market at the end of this year. Then, despite all the fuss, we’d feel we’d chosen a car that was clean, efficient, legal and fine to drive.

David Greenwood, head of advanced propulsion at Warwick University, says: “A two thousand sixteen EU6 car emits less than 1% of the particulates a similar car did in 1992. For NOx, the output is well below 10%. If you read some media, you’ll see headlines that say air quality is getting worse in cities. It’s not. The data says it’s getting better. But it’s not getting better at the rate we’d like it to.”

The bottom line is this: the cleanest diesel you can buy is very likely the one you’ll be able to buy late this year, which not only meets current EU6 standards but has also survived the latest WLTP ‘real-world’ test procedures. If you need an older car and are worried about urban pollution, go for a post-2014 EU6 diesel or a post-EU3 petrol model, two thousand five or later.

1. Do think about the kind of driving you do. Diesels, even older models, are fine if you don’t drive in high-pollution areas.

Two. Do consider an electrified or plug-in hybrid if you have a two-car family fleet. Your 2nd car can be a diesel. You may find your EV’s smoothness makes it your very first choice.

Three. Do spread the word that better times are imminent for diesels, brought by stringent standards and a better testing process.

Four. Do examine the facts about diesel vehicles and air pollution, and pass them on. Disinformation has the potential needlessly to menace jobs and cripple an significant industry.

1. Don’t get the idea that criticism of diesel cars is all wrong. There are at least seven levels of car diesel ‘cleanliness’. Only latest versions can truthfully be termed clean.

Two. Don’t abandon the idea of making your next car a modern diesel, however. Diesel sales are helping to supply vital targets for lowering CO2 and reducing global warning.

Three. Don’t accept assertions that steps already taken to cut toxic emissions and CO2 have not worked. There are figures to demonstrate they have. But there’s much more to do.

Four. Don’t presume that all diesels are bad. The latest types, for reasons listed, can be much cleaner and safer.

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