A pre-purchase inspection (PPI) by an independent, ASE-certified mechanic is highly recommended and considered one of the best ways to protect yourself when buying a used car. It helps uncover expensive hidden mechanical or title issues that can save you thousands in repairs, and the report provides essential leverage for price negotiations. If a seller refuses to let you have the car inspected by a mechanic of your choice, it is a significant red flag, and you should consider walking away.