Back in '09 & '10 I was working as an expat for Air india. We spent a lot of time in FRA and I would rent cars and drive. It may seem intimidating, but it isn't much worse than driving in an unfamiliar city in the USA.

I don't know if it is still available, but we used to rent cars from Lufthansa that they made available for their crews. If I remember correctly the car rental office was in their employee parking garage. Anyway the rentals were significantly less expensive than renting from a rental company. We stayed at the Intercontinental on the river in Frankfurt and I would ride the train to the airport to pickup the car and back when I returned it.

If you decide to drive you will pass the Technik museum in Sinsheim. If you are any kind of a gearhead, this will be the coolest museum you will ever see. They have both the Concorde and the TU-144 and so many other things I could not begin to list them. Sinsheim is about a 30 minute drive from Stuttgart.

Auto & Technik MUSEUM SINSHEIM | Car & Technology Museum Sinsheim | South Germany