The base Panamera uses a V-6 engine to score 18 mpg city, 28 mpg highway, and 22 mpg combined per the EPA. The somehwat sportier Panamera S scores 17/27/21 mpg. With all-wheel drive, the Panamera 4 rates 18/27/22 mpg. The higher-performance Panamera 4S downsizes the V-6 and adds a turbo to yield EPA ratings of 17/27/21 mpg, while the long-wheelbase Panamera 4S Executive scores just slightly lower at 17/26/20 mpg.
Moving up to the driver's choice, the Panamera GTS scores 16 mpg city, 24 mpg highway, and 19 mpg combined. The high-tech Panamera S-E Hybrid is rated two ways: with electric-only and gasoline-hybrid mode combined, it scores 50 mpg combined city/highway; in gasoline-only mode, it rates a combined score of 25 mpg.
The high-performance Panamera Turbo dips only slightly in EPA ratings in comparison to its non-hybrid counterparts, at 15 mpg city, 24 mpg highway, and 18 mpg combined. Kicking up the performance to Panamera Turbo S levels yields the same 15/24/18 mpg gas mileage, as does opting for the long-wheelbase version of the Panamera Turbo S.
Taken in the full context of its performance, size, and equipment level, the Panamera is not precisely efficient, but it's not the worst offender at the pump, either.