I got the following promotion email from United for renting Avis car:
Rent your car with AvisŪ on your next trip and save up to 35%
on your car rental and earn 125 MileagePlusŪ award miles
per day. Use United's Avis Worldwide Discount (AWD) number K019376.
Plus, earn an additional 1,500 bonus award miles on rentals of three or more days at participating airport locations in the U.S. and Canada. Use coupon number MUAA096. Discount and bonus miles offers are valid through September 30, 2012.
Plus: Earn 150 bonus award miles for booking an Avis car at united.com.