FLEET managers must see for themselves how their vehicles are performing at auction rather than rely solely on valuation guides if they are to make the most of their vehicles' values at disposal time, residual value and disposal experts are claiming. Hundreds of pounds could be wiped off a car's value while waiting to be sold because a fleet manager is attempting to achieve a 'book' value that may never be reached as residual values fall.

Not only that, but the market value of the car may be falling in real terms because it is ageing. If a fleet manager is selling direct to the trade, undervaluing the car because they do not understand the state of the current market, it could also cost them dearly. Disposals experts are warning fleet bosses they must keep close to the market to understand what is happening, so they can react immediately to make the most of their vehicles' potential value.

Ramesh Notra, economist for CAP Motor Research, which produces CAP Black Book and CAP Monitor, a guide to future residual values, said: 'I agree that these are guides and are not specific to every vehicle when it appears at auction. We pride ourselves on our accuracy and forecast what might happen over the next month in the market when producing the guides. However, it is crucial that vendors actually attend sales or have one of their staff keep close to the market to ensure they get a good feel of how the market is performing on that particular day and at that particular sale. This is something on which we have been trying to advise fleets for some time, because managing a sale properly can lead to a huge bonus at disposal time.'

Fleet managers have been the focus of a long-running campaign to ensure they react quickly to the changing attitudes of car buyers. British Car Auctions, Manheim Auctions, CAP Motor Research and Glass's Information Services warned last year that the practice of holding on to cars in a bid to get better prices was a mistake. At the time, vendors were getting £500 to £750 less than expected, but if they refused to sell and held on for their reserve price, the firm would still have to cover the holding costs of the cars in the meantime.

Mike Partridge, operations director of Motorauctions Leeds, said: 'We do a lot of business with large fleets. There are sometimes large differences between the two guides, CAP Black Book and Glass's Guide, which causes problems. Also vendors seem to assume a car is worth its 'CAP clean' value - effectively ready to retail - no matter what condition it is in. However, we do have a few fleets who attend every sale they can, not just ours.'

BCA's customer affairs director Tom Madden commented: 'BCA Auction View's values shown are updated daily and represent the pound note price for a fleet car. The published guides are just that - guides. They can provide the vendor with a benchmark against which he can judge his performance - that is all they can hope to do. They cannot be a price list and should never be used as such.'