Turbocharged and intercooled small displacement gasoline engines have a small fuel economy advantage
over same horsepower non-turbo engines
in that their BSFC minimum is over a broader range of RPM.

But if the system has an added battery hybrid drive, that also can also “broaden” the best Brake Specific Fuel Consumption range of RPM.

If the richer customer expects a V8 in a premium car,
and the expensive turbo and intercooler cost can be eliminated,
the almost the same EPA MPG window sticker numbers could be gotten.

Does any customer buy an AMG model for better fuel economy?