My understanding is that the AMEX SPG Platinum card provides a number of benefits, including rental car benefits. How does this work? For example, you receive a 1 car upgrade and complimentary membership in the priority club of a number of rental car companies. How does this work? Do you provide the rental car reservationist a code when making a reservation and request an upgrade? Do you need to complete special forms with the rental car companies to be included in their priority clubs? Hopefully, someone can help me understand the mechanics of this process. Thanks.