Ok - What car is making over 300hp and less displacement?
Ok lets use the Acura RL - it has 300hp and gets 18/26 BUT only has 260tq.
The GP has 300hp get the same milage but has 323tq - Hum.....
I understand your theory on the "power per liter" but usually the gas milage is around the same and I like the V8 sound a lot better. Also the 5.3L enginge is way down in its potential where as Acura's 3.5L is running near the edge of potential.
Power does not only come in "horses" is also comes in Torque