Oral contracts in car sales hold actualy little to no legal standing in a court. A written contract is legaly binding and only can be broken if a term of the contract breaks a law (such as ussurious intrest rates ect). You can say that the car would be a great drift car and it will not matter how rusted the chasis is. When buying a used car it is the buyers job to ensure the vehicle meets their standards. If the car is being sold in a as-is situation with no warrenty implied by the seller then your out of luck. Sorry but the loophole stuff mentioned as well does not have any standing in court. You sign a document and the contract meets the legal requirements then you are bound to it unless the seller breaks one of the terms listed.
Long story short you MUST get it in writting if you want it to be a term and condition of sale.