When renting a car, I have also found it useful to sleuth what special conditions might have been negotiated in any organizational rates to which I may be entitled. For instance, I like the USAA rates with Hertz and Avis because they cap the renter's maximum liability at something like $5k and have negotiated that the companies will not charge for lose of use when the vehicle is being repaired. They also allow another USAA member to be a second driver without being on the rental contract. Those are all useful benefits.

Also for anyone with a European Plat/Cent card, some of those negotiated rates with Hertz include the collision damage waiver free of charge along with the 4 hour grace period.

Thus when I price shop I always look first at the European Hertz AMEX rates and then compare with the USAA rates.

In any case, this is one situation I would not use organization rates to which I am not entitled because I can imagine the rental car company would deny those benefits in an accident if they realized the renter was not entitled to the rate plan.