New research has found that replacing diesel cars aged at least 10 years old or longer could slash the UK’s fuel consumption by as much as 173 million gallons, according to Kwik Fit.

Kwik Fit’s recent analysis of the nationwide car parc found that British motorists are now driving more than 30 billion miles a year in almost three-and-a-half million diesel cars (3,476,000) registered during or before 2007.

If all of these journeys were made in newer diesel vehicles – with greatly improved fuel economies – drivers would save £947.8 million a year in fuel costs. It would also result in a decline in HGV traffic, with diesel fuel savings equivalent to 20,700 of the largest full fuel tankers carrying 38,000 litres per tank.

The possible reduction in fuel consumption would also lead to a significant decline in CO2 emissions. Those decade-old cars which meet Euro 4 emissions limits would be replaced by newer diesel vehicles in the Euro 6 category.

Emissions of nitrous oxide (NOx) would fall by 8.2 million kg by switching to newer diesel models – a reduction of more than two-thirds (68%). Meanwhile particulate matter would decline by 970,000kg – an 80% reduction.

Roger Griggs, communications director, 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 reappear 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.”

Nevertheless, the estimated cost of replacing all diesel vehicles aged 10 years old or more with new models would be in excess of £97.3bn, assuming an average new car value of £28,000 per vehicle.

“Not only will better fuel consumption help reduce emissions and thus provide long term benefits, it will also immediately start to save motorists money,” added Griggs.