Diesel and petrol cars still make up the majority of UK car sales, despite gradually-increasing electric car sales in the UK. Diesel engines have had a tough time in the press lately and, while some of the criticism may be merited, there’s a lot of misinformation out there.
Most of the bad press was down to the VW emissions scandal, where real-world testing revealed that some cars’ emissions were far higher than they were when tested in lab conditions. It’s crucial to note that the problems outlined in this scandal affect older diesel models, and the fact modern diesels feature exhaust-after treatment such as AdBlue and diesel particulate filters (DPFs) mean they’re fully compliant with the latest Euro6 emissions standards.
Diesel-engine cars were promoted by successive UK governments for more than a decade because they have, on average, 20 per cent lower CO2 emissions and 20 per cent better official fuel economy than their petrol counterparts. These are important factors in helping to tackle climate change. However, the Government now needs to address the levels of pollution in our cities, because it is being sued by the European Commission for repeatedly breaching air pollution limits.
The nitrogen oxides (NOx) produced by diesel engines are one cause of air pollution. Although diesel-engined cars emit more particulates than petrol ones, their CO2 emissions are generally lower. It’s also important to note that older diesels have far higher particulate and CO2 emissions than newer ones, and that the EU has been tightening up on emissions since 1992.
The first Europe-wide emissions standards, applicable to all new cars registered from January 1993, set an upper limit of 2.72g/km of carbon monoxide (CO) and 0.97g/km of NOx for diesel engines. Significant improvements were made with the Euro5 standard that applies to cars registered after January 2011. In order to comply with the limit of 0.18g/km of NOx, diesel-engined cars had to be fitted with DPFs that capture 99 per cent of all particulate matter before it escapes out of the exhaust.
The latest diesel-engine cars (those sold from September 2015 onwards) comply with Euro6 regulations and are the cleanest in history. As well as being fitted with DPFs, they have systems that convert most of the NOx from the engine to largely harmless nitrogen and water; for diesel engines, their NOx emissions cannot exceed 0.08g/km. Now those Euro6 cars are starting to filter into the used car market so you can feel good about buying a diesel, because they are some of the cleanest cars out there and you won’t have to worry about being charged when you go into a Clean Air Zone.
Honda diesel models still retain the best MPG – Honda Civic 1.6 for example has an combined MPG of 78.5 MPG. Many Honda Diesel models, particularly the 5 door hatchbacks still qualify for £0 road fund licence.
If you are thinking of buying a used diesel it is worth checking which regulation the engine complies with, as some manufactures were complying with Euro6 way before they had to.