2025 Gmc Sierra 2025 At4 Mpg. With a 19 mpg city, 20 mpg highway, and 19 mpg combined epa fuel economy rating, meanwhile, the diesel isn't quite as efficient as it is in other sierra forms. Fuel economy of the 2025 gmc sierra 4wd at4x.
Detailed specs and features for the 2025 gmc sierra 1500 including dimensions, horsepower, engine, capacity, fuel economy, transmission, engine type, cylinders, drivetrain and more. With a 19 mpg city, 20 mpg highway, and 19 mpg combined epa fuel economy rating, meanwhile, the diesel isn’t quite as efficient as it is in other sierra forms.