Wow, I appreciate that information. The only problem is, I don't believe many places rent out hybrids. But I will definitely be on the lookout and see if this would work.

I drive the hybrid on days when mpg is important. I drive the Mustang on days when miles per hour is important.

Physical damage would not bother me as much as them "corrupting" the avg mpg display I tired to hard, and for so long, to get has high as possible. A renter could, in just one weekend, destroy all that hard work and return my hybrid with something like "avg 12 mpg" showing.

In the southwest US (CA, AZ, NV), Fox Rental has Prius and Civic hybrids for rent. I'm going out there in the spring and plan to rent a Civic then. It should be interesting driving on flat terrain for a change. I assume the mpg will be much greater than what I'm used to here in WV.

I thought that was interesting, Hybrid Eer, and I've never really heard of that car rental company, so I looked it up. The company is actually called Fox Rent-A-Car and if you click on the various locations on this site:
http://www.foxrentacar.com/FoxFleet.aspx
they show you the vehicle fleets available to rent from them at each airport location. If you click on SFO, they have both the Prius and the HCH pictured, along with the HiHy and/or the FEH. There's also a note:

Most impressive!

Some of their locations were surprising, like Kansas City, MO (no hybrids pictured), several in Florida, and even Anchorage, AK. It would seem that the hybrids are only really available in most of CA and Phoenix, though.