Used diesels are selling faster than their petrol equivalents, despite campaigns to shift buyers away from the fuel.
New data from Cap HPI reveals that diesel models are selling within 45 days while petrol models take 49 days, on average.
Derren Martin, head of UK valuations at Cap HPI, said: "Despite on-going negative coverage of diesel engines and a marked decline in new sales, the used buyer still has an appetite for diesel cars, which offer low cost of ownership and a driving dynamic that appeals to many."
The increased popularity could be a result of falling values for diesel cars. Average diesel car values dropped by more than petrol ones in June, and while the difference in value drops is not dramatic, says Cap HPI, it is a trend that has occurred in every month of 2019.
Petrol hybrids dropped in price by less than the average, and their popularity may well be on the increase in the used market at least.
The automotive data business says diesel still dominates the overall used car market in terms of volume, due to high registrations in previous years.
Cap HPU believes the used market will tip toward petrol for newer vehicles, due to the shift to petrol in recent years.
Martin said: "Despite high used volumes, and contrary to what is happening in the new car market, there has been plenty of demand for used diesels and used values have held up relatively well over the last couple of years.
"Used supply will fall off significantly over the next few years, and this will help to support used values over a period when demand is likely to fall too."
The company warns that if and when more cities implement charging or exclusion zones for older diesel cars then it could create local pockets where older diesel cars could struggle to sell, but they will still have a market, at a good price, in rural areas away from these cities.
According to the Vehicle Remarketing Association (VRA), new diesel car sales are falling so quickly that there could be shortages of them on the used market in the near future.
The organisation says that while new car diesel demand has plummeted, corresponding used demand has stayed relatively firm.
Philip Nothard, deputy chair at the VRA, pointed out that in the two-year period since Dieselgate, which was followed by the impact of WLTP, half a million fewer diesel vehicles have entered the used car market.