I've used the Car and Driver code in the past, but my rate always seems to go up with it. Maybe it's just my bad luck, but I've had this happen every time I've tried to use it instead of the generic Emerald code. In fact, I always seem to get the cheapest rates when using the generic Emerald code over any other code...including my corporate code.

Additionally, I always feel more comfortable using a code I am 100% certain I am authorized to use. I understand the C&D code is supposed to be safe for anyone to use, but I just feel better knowing there is absolutely no way I could run into problem in the unlikely event my rental is damaged/stolen.

Anyway, hopefully other people will find this perk as useful as I do!