I'll be renting a car for two days at Sacramento airport, landing time is about 48 hours from now. I'm "Gold Plus Five Star" and I usually use my Amex Platinum CDP because it seems to always give the best rate I can find. Yesterday when I went to reserve a car, it showed that all cars up to full size were unavailable, and what was available (Premium, SUVs etc) was very expensive - over $100/day. This morning I checked again, same situation. I tried some other CDP's and when I entered IBM's CDP (40000) suddenly Compact/Int/Std/Full sizes are all available at very reasonable rates.

I understand that using a corporate code when I'm not really an employee is risky. In this case it'll probably work to collect the car since I'm picking up at an airport and I won't have to go to the counter - but I could be in a bad spot if I get into an accident.

Is there any way around this? If the IBM code "unlocks" all the smaller cars, they must actually be physically available, so is there any other code (that I can more legitimately use) likely to make them available too?