I was recently looking for a rental deal and found this link at United. Thought I should post it here and at the Avis link. FWIW, I got a great rate using this code too!

https://www.avis.com/AvisWeb/JSP/US/.../us_united.jsp

Here's the rundown...

Mileage Plus Members:

Earn Double Mileage Plus Miles and save up to 10% on all qualifying rentals booked through avis.com. Simply provide your Mileage Plus/Avis Worldwide Discount number K019331 with your online reservation for travel before December 31, 2002. Then, present your Mileage Plus membership number at the time of rental at any participating Avis airport location in the U.S. and Canada.

Plus, you'll receive an additional 250 Bonus Mileage Plus Miles, compliments of united.com

At Avis, We Try Harder to ensure you receive the personal service and
attention that makes every rental quick and easy.