Where once a car's fortunes would be decided by its overall condition and whether it sported metallic paint, customers are now demanding luxury extras, including air conditioning, according to Glass's Guide.
Adrian Rushmore, managing editor of Glass's Guide, said: 'Trade buyers are becoming more selective. The price gap between cars in the right and wrong condition, specification and colours has widened.
'A good example is that buyers are more discriminating of cars without air conditioning.'
Buyers are able to be particularly demanding because there are so many varieties of model to choose from. In the new market, there are 4,600 models available to the new car buyer and these will all eventually end up on the used car market.
Rushmore said: 'The final decision rests with customers. If they want more choice, then manufacturers are sure to oblige.'
But all fleet disposal managers are being warned that prices could drop during the second or third week in November.
Rushmore added: 'For the remainder of November, there will only be sufficient demand to stop prices falling any further. It will not be until the first half of December that we will see prices starting to edge upwards.'
Glass's Guide values have dropped compared to last month by 3%, but the firm pointed out it was much less than the 4% to 5% fall last November.