I think, the decisive point is really in the warranty regulations, like "equal or better". You chose one (which may have been the most convenient to you at that

I think, the decisive point is really in the warranty regulations, like "equal or better". You chose one (which may have been the most convenient to you at that time) and went with it. Anyways, this is how you chose to fulfil the contract. Are you really going to "fix" this years later by a withdrawal? Who has ownership of the car?