Rising motoring costs and the credit crunch are cited by a third of used-car buyers looking to downsize to a smaller, more cost-effective vehicle.
A survey by Glass's Guide also reveals that a growing number of motorists are switching to diesel as a way of cutting running costs and reducing CO2 emissions.
Managing editor Adrian Rushmore said: "This new survey illustrates how attitudes towards higher-polluting cars are hardening. Household budgets are being squeezed ever tighter, and people are looking for new ways to cut costs."
He said that concern over running costs are not likely to go away, which will further boost demand during the short and medium term.
But he added a note of caution: "There are certainly benefits to driving a diesel, with greater fuel efficiency and road tax.
"But buyers need to be aware that these models tend to cost more to purchase than their petrol counterparts, and it can take years to recoup this investment through reduced running costs.
"It is advisable to calculate estimated annual fuel costs and depreciation, for example, before committing to a diesel-powered car."
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