No offense intended to anyone, but most people over pay for rental cars, and I am talking about with their preferred company, simply because they made the reservation incorrectly (as in the case of the OP who made a one day rental into a one day PLUS 2 hour rental, which is really TWO DAYS without checking closely), and without doing the proper research to find appropriate coupons, discounts, AWD numbers, etc.
The same SOMETIMES applies to airfares, except that is often a matter of tinkering with dates and times and sometimes nearby airports, and with hotels (I use Marriott) by not knowing publicly available reservation codes, how to split reservations to take advantage of lower rates for part of the time, instead of a higher rate that might only apply for a day or two but that gets spread across the whole reservation because the traveler did not play around with the dates a bit. This last hotel tip also often applies to rental cars.
Remember, one of the main reasons for FT is to help our fellow travelers with travel tips and money saving ideas.