If a used car dealerships offers any form of grace period for returns, it is to comply with state laws that protect buyers from high-pressure sales situations that push them beyond their means. This allows the buyer time to review the terms of the contract and the condition of the vehicle and cancel the agreement without any remaining financial obligations.
In general, federal cooling-off rules only apply to sales made by a sales representative at the residency or workplace of the buyer, with the specific intent of preventing the representative from extorting or manipulating customers. Since used car dealerships complete sales at their place of business, the presence of a cooling-off rule or return grace period falls to state laws and the terms of the actual sale contract. These rules allow the buyer to return the used car or cancel the agreement within a specific period of time, starting at the moment of the sale, without penalty.
Most states do not provide any such protection for buyers purchasing used cars, as there are already other regulations in place that control the requirements of dealerships to disclose the state and condition of the vehicle. Many dealerships also post notifications within the premises that declare whether the state has any cooling-off rules, though the lack of notification does not imply the lack of such laws. Buyers should discuss these rules with the dealership before signing a contract and agreeing to a sale.