I assume car sellers - especially for used cars - are negotiating in bad faith. It definitely seems to make the process less efficient. Standard advice is to get a car inspected by your own mechanic before purchasing. Dealers disclosing the results of an inspection and being trustworthy would be a more efficient process - it would avoid redundant inspections by multiple prospective buyers, and it would avoid people wasting their time on cars in condition that they didn't want to deal with, and it would avoid people who don't know how to play the game getting ripped off.