quote: Not exactly. If were to follow your example, and have a 2.0L turbo vs a 4.0L NA engine, with both engines having identical power curves, and drove them exactly the same, the turbo will come out with higher mpg. Granted, it would be a small difference, but it would still be there. The Turbo engine is almost always going to be lighter than the NA engine. Less mass requires less fuel to move it.
quote: On top of this, turbo engines are tuned to run rich. They must run rich to avoid detonation on pump gas, and this increases their fuel consumption.