One of the most used is BBK
I personal use to buy my last car and I made the seller lower the price because I have show him that I was prepare to win this battle for good deal
What is Kelley Blue Book?
Types of Values
The Trade-in value represents what you might expect to receive from a dealer for a consumer-owned vehicle. Keep in mind that the dealer must absorb the costs of making the vehicle ready for sale, so trade-in values are almost always lower than retail or private party values.
The Kelley Blue Book Suggested Retail value represents the amount an auto dealer might ask for a specific vehicle. The Suggested Retail value is a starting point for negotiation; therefore, the actual sale price will vary. A vehicle's popularity, condition, warranty, color and local market conditions are factors involved in determining a final price. This retail value is not a trade-in or private party value.
The Suggested Retail value assumes that the vehicle has been fully reconditioned and has a clean title history. The Suggested Retail value also allows for advertising, sales commissions, insurance and other costs of doing business as a dealer. Most vehicles offered at this price have passed an inspection, and some may carry a warranty.
Private Party value represents what you might expect to pay for a used car when you purchase it from a private party. It may also represent the value you might expect to receive when you sell your own used car to another private party.
Vehicle Condition Descriptions
"Excellent" condition means that the vehicle looks great, is in excellent mechanical condition and needs no reconditioning. It should pass a smog inspection. The engine compartment should be clean, with no fluid leaks. The paint is glossy and the body and interior are free of any wear or visible defects. There is no rust. The tires are the proper size and match and are new or nearly new. A clean title history is assumed. This is an exceptional vehicle.
"Good" condition means that the vehicle is free of any major defects. The paint, body and interior have only minor (if any) blemishes, and there are no major mechanical problems. In states where rust is a problem, this should be very minimal, and a deduction should be made to correct it. The tires match and have substantial tread wear left. A clean title history is assumed. A "good" vehicle will need some reconditioning to be sold at full retail price; however, any major reconditioning costs should be deducted from the value. Most recent-model cars owned by consumers fall into this category.
"Fair" condition means the vehicle probably has some mechanical or cosmetic defects but is still in safe running condition. The paint, body and/or interior require the work of a professional. The tires need to be replaced. There may be some repairable rust damage. The actual value of cars in this category may vary widely. A clean title history is assumed. Even after significant reconditioning this vehicle may not qualify for the Kelley Blue Book suggested retail value.