Originally Posted by AutoSlash

Hertz President's Circle entitles you to a one-class car upgrade only, so that means if you reserve an economy car, you'd be entitled to a compact car, and if you reserve a compact car, you'd be entitled to an intermediate car. With PC status, the location certainly might treat you better, but reserving an economy or compact car and hoping for a fullsize might be a bit too much to expect.

See here for more info.