I can only find this.
The highest end car you can get with this coupon is a Premium(when booking a Standard 2 door).
This is the sweetest deal, as in Austin you pay about 23$ for a standard for a weekend rental and a Premium is 38$!! And these are AAA rates!! You can also book a Compact and get a Standard(Mustang).
This offer is valid till April 30 for people charging their rental using AMEX.
Mention coupon code 927334.
If you are a AAA member you can also get an additional 10% off.