IF there was a valid agreement made *when you bought the car* that you could return it within 30 days, that agreement is enforceable. Where you could get into trouble and be in breach of the sales agreement are:1) If there was no return provision in the sales agreement when you bought the car, then the rep probably could NOT after the fact give you the right to return it--there would be no consideration for her doing that, and she could necessarily unilaterally alter the contract or agreement after the fact. So if when you bought it was nonreturnable, you probably can't return it.2) Even if the rep made statements that you could return it within 30 days prior to your signing the sales agreement, if that term did not make it into the sales agreement, you can't enforce it contractually--it's not part of the contract of sale. In this case, you *may* be able to rescind the contract on the basis of fraud in the inducement--that is, that material (important) misrepresentations (lies) were made to induce you to buy the car. However, as a practical matter, it may be very difficult to make and sustain this case if there is no evidence of that discussion and meanwhile, there's a sales agreement which doesn't mention it.