If you put that question into Google, you get the answer that turbo engines have better mpg, but I remember reading that, during the development of Ford’s 7.3L gasoline engine, they came up with some kind of formula that calculated the most fuel efficient engine for a medium duty vehicle was the N/A 7.3 they ended up with. I’ve also heard it from some of my engineer friends. So what is it?
Totally depends on application. If it’s in a performance application, then the turbo exists to allow more fuel to be burned for more horsepower.
If it’s an economy application, the turbo exists so the engine can be smaller and burn less fuel most of the time, but still have adequate power when it needs it.