I had this same problem lately. My solution since it was a pleasure trip and I wasn't going anywhere but the town I was in was to Priceline the first day and then pick up the weekend rate next day. Of course I had to turn in the car and pick one up, but I saved $80 plus. This was at National and I am Emerald Club so it wasn't hard to do at all. The one day I picked up on Priceline was an Alamo rental (sister company) and I ended up with the same type car both days. At that airport all the cars are on the same lot anyway.