Used diesel cars now account for around four in 10 second-hand vehicle purchases, according to new figures from online car supermarket BuyaCar.co.uk. The company says used diesels made up around 30 percent of transactions in the summer, but that figure has risen to 38 percent in October and early November.

The figures come despite what BuyaCar.co.uk called “significantly higher” availability of petrol cars compared with diesel models. Even the fact BuyaCar claims its customers tend to spend more on used diesels than second-hand electric cars could not prevent the much-maligned fuel growing its market share.

And the new trend also comes amid a surge in popularity of electric cars, with searches for battery-powered vehicles also up on the BuyaCar website.

Potential used car buyer inspecting door

BuyaCar’s analysts have suggested that brand image could be a contributory factor in the popularity of diesel, with Mercedes-Benz dominating the market. According to BuyaCar’s figures, Mercedes-Benz has a bigger share of the used diesel market than any other manufacturer, but the likes of Ford and Vauxhall offer more petrol models.

Although electric car prices are often cited as a barrier to adoption among consumers, the figures suggest BuyaCar customers are choosing diesel cars even though they are typically more expensive than the electric vehicles (EVs) bought on the site. And the diesels they choose also tend to have higher mileage than the cars of other fuel types bought on BuyaCar.

Volkswagen Diesel

“The strength of diesel sales may seem surprising at a time when all the headlines are about the rise and rise of electric cars,” said Christofer Lloyd, the editor of BuyaCar.co.uk. “Even more unexpected is the fact that although EVs tend to have a reputation for being more expensive than cars with an internal combustion engine, our customers are spending more, on average, when they buy diesel than electric.

"We have reported often on the enduring popularity of the Mercedes brand among BuyaCar's customers and that shows no sign of diminishing, even as the wider market changes. The majority of Mercedes buyers go with diesel, 31 percent of diesel buyers opt for a Mercedes and the top four sellers for diesel are all Mercedes, so the brand appears to have an outsized impact on the strength of diesel sales.

"But with the phasing out of all new diesel and petrol engines in the next few years it will be interesting to see whether Mercedes EVs can maintain the brand's particular appeal in the online used car market."