I recently learned that one can earn 250 miles after three parking visits at Thrifty on a variety of airlines, including UA, US, TW, CO, DL and others. One can also earn hotel points instead.
http://www.thriftynorthwest.com/airm...RMILE2000.html

If you are a frequent denizen of Thrifty parking, ask the attendant to give you a punch card to keep track of your visits.

I had heard quite some time ago that Thrifty offers miles for parking as well as renting but none of the attendants in PDX ever seemed to know anything about it when queried in the past. According to the very friendly agent at 1-800-777-4761, you can
collect your old receipts and mail them, accompanied by your FF#, to

Thrifty Frequent Flyer
PO Box 35250
Tulsa, OK 74153