Diesel cars emit more pollution in cold weather, study finds – Telegraph.co.uk
Millions of diesel cars on British roads are emitting more pollution when the weather is cold, new research has revealed.
Testing company Emissions Analytics found emissions of poisonous gasses from many popular vehicles are far higher when the temperature outside drops below 18C.
The firm tested 213 models across 31 manufacturers and found the problem is worst among cars approved between 2009 and 2011, known as “Euro 5” cars.
As vehicles could be driving around much of the time with their pollution controls partly turned off, it means people are likely to be creating more air pollution by choosing to drive over walking or catching public transport than they currently realize.
But manufacturers claim the practice is legal and that cars are deliberately designed way to prevent them breaking down.
European rules allow manufacturers to cut back on pollution controls as long as it is to protect the engine.
Experts warned that without the technology drivers would be at a higher risk of parts of their car breaking, leaving them with large bills for major repair work.
Nick Molden, chief executive of Emissions Analytics, said: “I would say from the Euro 5 generation of cars, it’s very widespread, from our data. Below 18 degrees, 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”.
The Society of Motor Manufacturers and Traders, which represents car makes, told the BBC: “The temporary reduction or switching off of some emissions control systems under certain temperatures is allowed by law and necessary to avoid damage to vehicles’ engines.
“Without it, there could be a significant cost to the consumer for major repair work. In its recent report, government recognised the need for such technology and was satisfied with how vehicle manufacturers were using it. Manufacturers are investing billions of pounds in developing ever-more advanced technology, and this along with new Real Driving Emissions regulation from next year will see significant lowering of emissions across a full range of driving conditions and temperatures.”