just booked 7 days in jacksonville florida for base rate of $82 for a mid-size. Used contract ID 7013603 (got $19 off) AND coupon AD3829MRB (another $25), unbelievable. YOU WILL SEE ALL YOUR DISCOUNTS ON THE SECOND SCREEN. I plugged codes for hours and found nothing to beat it.
costco code 7013903 (note one digit diff than above code) worked good too along with coupon combo but it still came out $3 higher above.
Also you can sub coupon au4874odg to get one car upgrade instead of $25 off.