I have some expiring United mileage that I'd like to use to purchase a few "free day awards" to apply toward a 5-day one-way car rental for a family trip this summer. However, I can't figure out definitively if the car rental co. (Budget, in this case) will accept them toward the rental.

The Mileage Plus web page where you redeem miles for a car rental has a form that permits you to enter the date, number of days, and pick-up location of your rental, but not the drop-off location.

I'd love some insight from someone who has used this system. Is this form used to actually make a reservation? Or just to buy a series of free day awards? Are the free day awards applicable to a multi-day rental?

I have already reserved on the Budget website. The Mileage Plus customer service rep in India insisted that I should go ahead and purchase the awards and then "call your rental car company and explain to them." The Budget toll-free customer rep was optimistic that the award would be accepted. To reassure myself I called the Budget office at PDX and the rep there said that she was not sure.

Thanks in advance for your help!