Q. What book value is used by dealers as the authority on car values?
A. Dealers have different sources of wholesale (or trade-in) values, and they're free to use any or all of them.
The Kelley Blue Book is probably the best known. But there also is the Black Book, a price and data service available to dealers and others in the auto industry, and NADA Guides, an affiliate of the National Automobile Dealers Association. In addition, dealers may have access to used-car values beamed directly from wholesale auctions, giving them the latest prices for a vehicle they're about to take in trade.
Some dealers may use more than one of these sources to decide how much to offer you on the vehicle you're trading in (and perhaps how to price it if they decide to sell it on their own lot). There are probably still some dealers who fly by the seat of their pants and set trade-in values based on years of experience.
So which one should you use? We would suggest starting with Kelley Blue Book and then checking the NADA Guides and Black Book for comparison. (Black Book does not have its own consumer site but can be accessed through other sites.)
Don't be surprised if the results are different from all three. For example, we looked up how they value a 2008 Honda Civic EX with 50,000 miles in the Chicago area and found trade-in values for one in "clean" or excellent condition that ranged from $11,150 (Kelley Blue Book) to $11,250 (Black Book) and $11,850 (NADA).
Even if you own that particular Civic, that doesn't mean a dealer will offer you any of those three estimates because, as they say in the used-car business, every car is different, and one value doesn't fit all. Moreover, dealers want to make a profit on wholesaling a trade-in, so they're likely to offer you less than "book value." Bottom line: Used-car values, no matter what the source, are only guidelines. The real value is how much someone is willing to pay for it.