The increase in average used values of diesel cars in August was more than £200 higher than the rise in average values of petrol cars. This is a result of the fall in the pump price of diesel in late July.

Monthly sales data from Manheim shows that while values of petrol cars in the used market rose by 1.1% (£37.97) in August, compared to the first six months of the year, the prices of used diesel cars were up by 3.1% (£242.44).

Michael Buxton, chief executive of Manheim UK, said: “Although there are many variables around prices changes, including volume mix, age and mileage, it appears that the fuel price drop – the first time diesel has been cheaper than petrol since 2001 – may have already had an impact in the used car market.

“The average diesel car sold by Manheim was two months younger than in the previous month, with the average petrol car only being one month younger.

“However, the volume mix swung 0.6% towards diesel cars in August, which may have negated any residual value benefit from vehicle age.

“As we enter the new 65-plate registration period, it will be interesting to see whether the fuel price difference has any impact on new vehicle registrations, and whether we continue to see this trend reflected in the used vehicle market.”