Originally Posted by AutoSlash

If you are a PC member renting a car from a location where UC is not offered, the maximum upgrade you are officially entitled to is up to a full-size car, although it's at the discretion of the location to upgrade you from say a full-size car to a premium car. Reserving anything else--suv, minivan, convertible, pickup, etc. gets you the exact vehicle you reserved. The eligible upgrades only apply to economy through standard cars.