I did this a few years ago, when it was carsponsorships.com, which seems to just be a slightly different front for the carsponsors.com now, and when it was free to do. Now it says my account doesn't exist.
But anyway, when I did it, they didn't really have anything of real value, and most everything was just discounts, and not necessarily the stuff I wanted on my car.
Hope it's better now. Let us know how it turns out.