A new study suggests that drivers of the cleanest diesel cars are being unfairly penalised as their emissions fall well within the latest standards and are as clean as petrol-engined models.
The latest figures from Emissions Analytics – which add weight to the argument that government and cities are over-penalising diesels – show a number of diesel cars which emit less NOx in the real-world than the Euro 6 regulatory limits, including the first tested under the new Real Driving Emissions (RDE) regulation.
However, the study also found that other diesel cars were 10 times over the legal limit. The worst-performing 10% of diesels tested since January 2017 emitted 911mg/km, whereas the best 10% emitted just 61mg/km.
Emissions Analytics, which is expert in the use of Portable Emissions Measurements Systems (PEMS) and the interpretation and analysis of real-world data, declined to say which were the best and worst polluting diesel models or reveal their brands.
Nick Molden, CEO and founder, said:
“The most efficient diesel engines continue to improve while some of the worst remain on the market, meaning the confusion for buyers increases rather than diminishes.
“Diesel sales are falling as a result and this may lead to cities and governments over-compensating and restricting diesels more than is justified by our evidence.
“The danger is that motorists who bought genuinely clean diesels – together with the manufacturers who made them – suffer the consequences of the general confusion and loss of confidence.
“We should be alert to the consequences for carbon dioxide and particle emissions as the new car market seems to be shifting back towards petrol cars,” he added.
The new figures in the Emissions Analytics’ EQUA Index shows the best-performing diesel engines emit less than 80mg/km, well within the 2.1 conformity factor limit of 168mg/km.
Yet in contrast, the worst-performing 10% of diesels emit 911mg/km or more.
Across the Euro 5 and Euro 6 emission testing stages, the best 10% of diesel engines emitted 46% less NOx than the 10% dirtiest petrol vehicles.
In the UK, all diesel cars – including the best-performing ones that have achieved Emissions Analytics’ EQUA Index ‘A’ or ‘A+’ rating – will be subject to increases in Vehicle Excise Duty and Benefit-in-Kind tax from this April.
The Autumn Budget Statement last November revealed a rise in the diesel car benefit-in-kind tax surcharge from 3% to 4%, as well as a VED surcharge for new diesel cars first registered from this April. The First Year Rate will now be calculated as if cars were in the VED band above.
Under the changes, all diesel cars that have not been tested to Real Driving Emissions step 2 (RDE2) standards will face the higher company car tax and VED. However, currently, no vehicles have yet been tested to the new standard, which means all will be subject to the new charges.
Recently, Professor Dame Sally Davies, the Chief Medical Officer (CMO) for England, called for immediate action to address and avoid the negative health impacts of pollution.
In her annual report, the CMO recommended that government’s national standards for air pollutants should be increasingly stringent while being transparent and easy for consumers to understand.
Many of the recommendations revolve around the need for evidence-based action, along with a standardised approach to pollution surveillance and road charging to give vehicle drivers a simple and consistent system.
The EQUA Index, which is recommended in the CMO’s report, provides drivers with a simple way of understanding a car’s on-road NOx emissions.
The Index awards every car on sale today a rating from ‘A+’ to ‘H’ depending on the amount of NOx it produces in the real world, contributing towards a better understanding of the contributing factors of air pollution caused by engine emissions.
Nick Molden commented: “The current lack of trust in car manufacturers is not to the benefit of them, consumers, the market or society. A further recommendation of the Chief Medical Officer’s report calls for transparency on the part of the industry as to the polluting effect of their activities. Emissions Analytics believes this is a necessary first step to rebuilding that trust.
“We at Emissions Analytics hope the simple, independent and free-access nature of the EQUA Index is a good place to start to reassert evidence-based policy and the health of the automotive industry,” he added.