Originally Posted by
IAHtraveler
I find it best to just go through a handful and see what's best on those. Sure, if I tried 200 on every rental, I might save a few bucks, but my time is more valuable than that. For my locations/days, I've found the best recurrent success with one of the following: Costco, HHonors, AAA, United, my employer and another one or two. So I just try these, as I'm qualified for them all, and see what's best.
Just make your reservation with the best code you can find easily and then submit it to autoslash.com. If they can find a better rate they will notify you. In my experience, they often do!