Replacing 10-year-old diesel cars could reduce national fuel consumption

New analysis¹Â of the national car parc, released today by Kwik Fit, reveals the potential benefit of removing the oldest diesel cars from UK roads.

Researchers for the country’s largest automotive servicing and repair company have assessed the latest government national car population data and found that replacing all the diesel cars more than 10 years old with the latest models could save around 173 million gallons of diesel per year.

The nation’s motorists are currently driving around 30.2 billion miles each year in approximately 3,476,000 diesel cars – an average of 8,676 miles each – which were first registered in 2007 or before. With the improvement in average fuel economy over the last decade, if these same journeys were made in brand new diesel cars, the total savings which drivers would make on fuel costs would be in the region of £947.8 million per year.

There would also be a reduction in HGV traffic, as the fuel saving is the equivalent to over 20,700 full loads of the largest fuel tankers, which carry 38,000 litres each.

With the potential reduction in fuel consumption would come a significant drop in emissions as the older cars which met Euro 4 emissions limits (at best) would be replaced by those meeting Euro 6 requirements. Nitrous oxide (NOx) emissions from this group of cars would fall by 8.2million kg (from an estimated 12.1million kg to 3.9 million kg), a 68% reduction. Particulate matter (PM) would fall by 970,000 kg, an 80% decrease, dropping from 1.2million kg to just over 240,000 kg.

As recent data has shown², in real-world driving conditions many cars are not meeting the relevant Euro emissions limits. However, the researchers believe that the improvement in real word performance over the last decade mean these figures are a conservative estimate of the potential reductions in emissions from replacing diesel cars over ten years old. Indeed, the analysis is based on all the older diesels being replaced purely by cars with new diesel engines, whereas the reality is that many will be swapped for electric or hybrid vehicles.

A recent study by Kwik Fit found that only a third of diesel owners would buy another diesel vehicle when they replace their current model³. With many drivers indicating that they may switch to petrol for their new car, the researchers assessed the impact of swapping diesels over ten years old for new petrol models. If this switch was made, there would be an even greater saving in emissions over the same mileage, with the level of NOx falling by 9.2million kg, while the fall in PM would be the same as with a switch to new diesels. However, there would be a trade off as there could be a 24.3million kg increase in the level of carbon monoxide (CO) emissions, due to the CO limits on petrol engines being higher than for diesel.

Roger Griggs, communications director for Kwik Fit, said: “There has been a lot of discussion about the potential impact of a scrappage scheme in the fight to reduce emissions, and many manufacturers have been running their own individual incentives on new cars. However, the environmental benefits of these incentives are unclear, as many of the vehicles traded in under these schemes may simply re-appear on the second-hand market. This analysis reveals the impact which a national scrappage scheme could have on emissions, assuming the older diesel vehicles were permanently removed from the road and replaced with new diesel models.”

The cost of replacing all diesels more than 10 years old with new models, assuming an average new car price of £28,000, would be in excess of £97.3 billion.

Roger Griggs continues: “Clearly there would be a significant cost in replacing the oldest diesel cars and currently, this cost would be born solely by the individual motorist. Any incentives the government can give the private individual to move to more efficient vehicles could have a significant impact. However, we know that for many, buying a new car is not possible and so we would encourage all owners to ensure that their car is running as efficiently as possible. This will be helped by regular servicing, ensuring tyres are at the correct pressure and driving as smoothly as possible. Not only will better fuel consumption help reduce emissions and thus provide long term benefits, it will also immediately start to save motorists money.”