2013 Double Upgrade car rental codes
 

For those of us who use rental cars alot, I compiled this list

These all appear valid and to work, most came from rental sites themselves

Some may require "present coupon at counter" but that has never happened to me. Input the below codes on the rental car websites in the respective input areas on the site.

AVIS – CostCo One-Class upgrade and 25% off base rate
ID 7014627 , Coupon Code AU2291VYT

BUDGET – Double Upgrade and 20% off base rate
Offer Code/”BCD Code” U109200 , Coupon Code UUGZ011
For “La Quinta Inn customers”

NATIONAL – Double upgrade
Coupon ID NU3210FPI

HERTZ – USAA Double Upgrade Discount Code 77694 , PC Coupon 159530

Good stuff! Thanks!