Originally Posted by
AutoSlash
It's true for any discount code you don't actually qualify for. It's probably worth checking for discount codes you do qualify for (Costco, USAA, Southwest Rapid Rewards members, American Express cardmembers, etc.) as the rate my not be all that much higher and then you don't have to worry about being challenged at the rental counter.
FYI, I rented in PHL recently and they have a sign near the Preferred Desk agents that basically says, "AWDs xxx, yyy, zzz, ... require proof from their employer before the contract is printed". There are at least half a dozen AWDs listed, two of them that I've seen in this thread, so be cautious using AWDs one doesn't qualify for.