Acutally, most dealers I know use their own experience and AUCTION information to determine the best trade-in price for a vehicle. But that wasn't your question, was it. Between NADA and KBB, the differences vary from month to month. Sometimes KBB is higher, sometimes NADA is higher. I think KBB takes more into consideration than NADA does. It gives the opportunity to rate the vehicles condition, and additional options that NADA does not allow for. Being in the car business, however, we also remind customers that both of these services provided are GUIDES as to what a vehicle may be worth when trading it in. No dealer is going to open up their NADA book and give you dollar for dollar what it says. They may give you less, they may give you more. Here are some scenarios: Vehicle have around 50,000 miles on it? Unless you can PROVE that you just had the brakes done (rotors, pads, calipars) we deduct $500 for a brake job that we will have to do before we sell it. Some scratches in the paint? If, when you rub your fingernail across the scratch you don't feel it...it can be buffed out by the detail department. If there are A LOT of those kinds of scraches, expect another $300 - $500 in buffing. If your fingernail can feel the scratch, then the panel will have to be sanded down and repainted. Then you're talking a $200 - $500 per body panel. Does the air conditioning blow COLD? If not it will have to be FIXED, not recharged...FIXED. That could cost anywhere from $200 - $1,200. How's the interior? Does it smell of smoke? Dog hair? Stains in the carpt? Are there all 4 floormats? All this stuff will have to be fixed or dealt with by the dealer before its put on the lot "for sale" (Detailing costs over $100 usually. Factory floormats cost $75-ish) (If there is a stink that the carpet shampoo doesn't get rid of they have to use special cleaners that also cost more money) What about the tires? Are they in good shape or worn? Would YOU buy a car with tires that on it? If you wouldn't, then the dealer will probably have to replace those, too. Expect $300 - $1000 (depending on the kind of tire) How 'bout the exhaust? A little loud? Budget another $150 or more to fix that. Anything else?.....Glass, bulbs, the radio, etc. So, that 2004 vehicle that NADA gives you $8,455 trade in value for. Start deducting...what's wrong with it. If NOTHING AT ALL is wrong with it, then you might have a chance of getting what NADA is calling it for. But, if you expect the dealer to give you what NADA or KBB says your trade is worth, also expect to pay what they say the new vehicle's MSRP is. And after ALL THAT remember that what is happening in the market supercedes all that the GUIDES have to say. For expample: In my kneck of the woods a 2-wheel drive truck is useless. NADA may say that it books for big money...but even if I take it in on trade its going to sit on the lot until its not worth what we have in it..... So, to me a 2006 2-wheel drive truck is worth pretty much $0, regardless of what the guides say it is. And if you say that the dealer should just "take it to auction" then we go back to my first paragraph that says THATS what we should go by. Because, why in any situation, would you sell something for less than what you paid for it? (Which is what consumers want car dealers to do all the time)