From all the posts on this site, it sounds like Oase is unarguably the best FKK in Frankfurt. Can someone recommend the best approach to get there if I don't have a car and am staying near the train station? How much is a taxi ride, or should I rent a car? Is it near a train station? Thanks!

take the S5 train from Frankfurt Hauptbanhof to Bad Homburg or Friedrichsdorf (about 25 minutes).  Then taxi from there.  Taxi from Bad Homburg about 12-15 euro.  Taxi from Friedrichsdorf about 8-10 euro.  A taxi from Hauptbanhof is about 40-45 euro.  Enjoy!

Thanks vl4.