I usually get a great corporate rate with Avis, and it's rare that anywhere else beats it, including Costco. I do look up the Costco coupon code though (it's in the fine print), and apply it when I book directly with Avis. I've done this numerous times in several different locations, and it's never been questioned. I *am* a Costco member, so I figure it's legitimate enough. It usually saves me an extra $30 or so on a week-long rental. Just something to consider trying for those who book at Costco but continue to shop around!