When I use an upgrade coupon with National, it changes the reservation to be "counter" instead of "Emerald Reserve". I do not want to have to wait in line at a counter, or take a chance on them not having the upgraded size car, so I decided not to use the upgrade coupon. (The coupon states subject to availibility on the upgrade, so I take that to mean you're only guaranteed the smaller size car, which definitely would not work for us.)