I've usually found that it's only $5 or so more per day for a full size over an ecobox. Granted, the full size isn't always marvelous (Sonata, anyone?), but an upgrade from a full size is much better than an upgrade from an economy. However, if you really want a full size, I think if you reserve a "Standard" you'll usually be upgraded. The only standards that have been reported are the Fusion/Milan twins, and they aren't on Avis lots much anymore, unfortunately! The Edge is based on the Fusion, so I like it nearly as much!