Originally Posted by Gardyloo

Especially since you're talking about hiring convertibles etc., a big cost-saving consideration is that rental/hire car companies in the US charge enormous one-way or "drop" fees for cars rented in one city and left in another. For the (sorry) stereotypical Brit-in-a-Mustang trip in California/Nevada, this can add hundreds of dollars to the car hire price, a surcharge that can be avoided by returning the car to where you got it.