Diesel more polluting below 18C, research claims
News
22 Jun 2016
The BBC has reported that Emissions Analytics (EA) has advised that the level of pollution emitted from a number of popular diesel cars is higher when the temperature is less than 18C.
The research outlined that the issue was worst in models in the Euro 5 category of cars, which became mandatory in 2011.
EA tested 213 models across 31 manufacturers and found that temperature played a significant role in the performance of the vehicles’ pollution controls. However, European rules mean that cars can deliberately use this design to protect the engine from overheating.
Engineers have agreed that hot and cold temperatures can damage components. However, critics have suggested that car companies are taking advantage of the rule, which allows them to cut back on pollution controls, claiming it allows manufactures to improve the miles per gallon of the car.
In an interview with the BBC, Nick Molden, CEO of Emissions Analytics, said: "I would say from the Euro 5 generation of cars, it's very widespread, from our data. Below that 18 degrees [Celsius], many have higher emissions... the suspicion is, to give the car better fuel economy.
"If we were talking about higher emissions below zero, that would be more understandable and there are reasons why the engine needs to be protected. But what we've got is this odd situation where the [temperature] threshold has been set far too high, and that is a surprise.”
Official data shows there are around 5.1 million Euro 5 diesels on Britain’s roads. The EA report found that the average Euro 5 vehicle was 3.6 times over the legal limit for Nitrogen Oxides (NOx) above 18C, and 4.6 times over the limit when the temperature dropped below 18C.
The news comes as similar tests have been carried out by German, French and UK governments which identified similar findings.
A spokesperson for the Department of Transport (DoT) commented: “If we were talking about higher emissions below zero, that would be more understandable and there are reasons why the engine needs to be protected. But what we've got is this odd situation where the [temperature] threshold has been set far too high, and that is a surprise.”
