stvr

I used a pretty neutral Priceline AWD to save a small percentage on a one-day rental. Also inputted my Southwest # and was billed $1 plus tax for the miles as a FF surcharge.

Two months later and no miles...

I call and they tell me the AWD is ineligible.

"Why was I billed for the miles then?"

She said it's because they STILL have to interface with the airline and the cost of that needs to be defrayed.

Took MANY escalations before I got my $1 plus tax refunded for the missing miles.

Still don't have an answer about how to find if your AWD invalidates miles. They will bill you anyway. Makes me lean a little more in the direction of Hertz/National, where I haven't had such a problem (using some pretty crazy codes, I might add).

sdsearch

Save a small percentage relative to what?

Did you compare the Priceline AWD against several airline AWDs, or only against no AWD at all?

I can't give you an answer as to what AWD invalidates miles, but I can give you a simple list of AWD that work with miles:

Every airline program and hotel program AWD works with miles/points (including of other airline and hotel programs).

In my experience, the biggest key to low prices is not the exact AWD, but the exact day that you finalize the reservation. Generally the best price seems to be somewhere between 2 weeks out and 1 day out, and the more time you can check to see if it's worth the "Modify My Reservation" during that time, the more likely you'll save (more than by using a different AWD three weeks out and then never repricing).

Having said that, I have saved money in the past by using an AWD for airline X while earning miles from airline Y. So it's worth checking a few different airline (and/or hotel) AWDs, not just the one for the airline whose miles/points you're want to earn on that rental.

stvr

To save a small percentage relative to the next cheapest AWD. The code shaved like 30-40% off the price. Other AWDs would have been 20%. Definitely wasn't worth "paying" for the miles by paying extra for the car.