I have the Same Problem, but my FPS ar not increasing in time. My Framerate is fix at 10-20 FPS in one (!) Savegame with a low amount of BUildings and no Vehicels. In other Savegames the Framerate is at 30-50. Its only this one Savegame, where i Build my Base on the pink Plateau. I Changed all my Settings but nothing worked. I overclocked my Videocard and CPU an it didnt worked.