Rising residual values for diesel cars has led Glass's Guide to proclaim a 'new era' for oil burners.
It puts the cause down to the recent fuel crisis as high pump prices focuses drivers' minds on fuel efficiency and the pence per mile benefits of diesels.
And the bigger the car, the greater the differential between diesel and petrol used car values.
Glass's Car editor Johnathan Brown said: "We are entering a new era for diesel cars. Vast improvements have taken place in diesel technology, especially over the past two years Whatever the fate of the new car market, used car buyers have already given their vote of confidence.
"It is possible to look at any sector of the market and find startling differences in favour of diesel. The only real exception to this rule is for small cars, where it is rare to find differentials of more than £150."
Examples of the average gap between diesel and petrol in the nearly-new sector include £500 for a Ford Focus, £1,800 for a Citroen Xsara, £2,000 for the Volkswagen Golf and £4,950 for a Mercedes C Class.
However, Mark Cowling, chief economist at Cap Motor Research said: "It's easy to overcook the market. If prices are too high, used car buyers will realise they are not doing enough miles to make back the money in lower fuel costs."