Outfitted with a PDK transmission, the base Carrera is the most efficient offering, at 20 mpg city and 28 mpg highway--very respectable figures for any daily driver. At the other end of the spectrum is the Carrera 4S with the seven-speed manual transmission, rated at 18/26 mpg. The other 991-based models fall somewhere between those bookends.
Of course, there are still 997 models being sold, and being based on older designs, as well as being the highest-performance variants, they are somewhat less fuel-efficient. The 911 Turbo S Cabriolet, for example, manages just 16 mpg in the city and 24 mpg on the highway.