Porsche Certified Pre-Owned Certified. Navigation! The convertible you've always wanted! When's the best time to buy a convertible? When summer is gone and dealers are looking to give them away! Like us! Look at the miles, look at the options then look at the price! Buying an used car can be a risky proposition, but with the protection of pre-owned certification, you won't be left out in the cold as soon as you drive off the lot.