Costco Travel advertises it differently:

Budget Rent A Car
$40 Off & Save Up to 35%


Valid for Travel Through 12/15/2013
Book by: 10/15/2013
Minimum rental: 5 Days
Terms & Conditions


BCD Code: W852873
CouponCode: MUGZ041

Although the terms and conditions say September 30, the rate is accepted for October travel dates, and says expired on December 15 if I try January travel dates.

I would cross my fingers and use it for our October trip (we are Costco members regardless)