Like Ard said, was there any facts misrepresented before the transaction occurred, otherwise you would have acted differently. it depends what conversation you have with seller leading to your purchase. you need to have at least 2 appraisals that reflect the diminished value. 1 could be from Carmax, 2 must be from a Certified Automobile Appraiser, you need a reputable one for this. (Cost you about $300). Once you have these appraisals, you need to send a demand letters with certified to the legal name listed for the dealer, explaining why you write the letter and what solution you're seeking, give them 14 days to response. Don't forget to include a copy of the appraisals, two Carfax reports. Keep all the records for yourself. If no response after 14 day, then send them a second letter, tell them same thing from your first letter, but this time you let them know that if you don't here from them in 10 days, you will considering legal action against them, don't threaten if you don't plan to follow through. A lots of time consuming and patience. Those are the steps that you have to do for now, and wait for their response, if you have to go this way. Believe me, auto fraud attorney would love to take dealers to court, if you have a case.