cool things with wheels, since 2006
I guess Ford's marketing people didn't run the Taurus ad by their engineers. If you add more air to the engine, you have to add more fuel to keep the right air/fuel ratio. Just adding more "free" air would make a lean mixture, and the engine wouldn't be happy with that.
Turbos get scads more power, without affecting the gas consumption much. The Koennisegg makes 1300 hp from a 309 cu in, 5 liter, twin turbo, in 2015, the 2016 makes 1489. Ford's 5 liter makes about 1/5th of that without the turbos.
You are correct that a turbo charged engine can use less fuel at low-load conditions, which allows a downsized turbo 4-cylinder engine to get better gas mileage than a 6 cylinder with the same horsepower. Or turbo V6 compared to a V8 in the Ford ad. But if you are using all of the available power, you still need fuel to go along with the air that the turbo is pushing into the engine. If you add more air/oxygen to the engine by adding Nitrous, supercharging or turbocharging, you have to add more fuel by using a larger carburetor or bigger fuel injectors. If the Koenigsegg is using all of those 1489 hp, it will drain the fuel tank quickly, but if is just running 55 mph on the highway, it probably gets decent mileage.
would you agree that the same 500 hp on a turbo v6 will likely use less fuel than 500hp on a v8 without turbo?
That is probably true, because the turbo will make the engine operate more efficiently. My main issue was with the ad writers saying "air is free", like the engine isn't using any fuel at all.