Originally Posted by erhanh
M cars are not about efficiency. Maybe I'm wrong, but trying to have high revving engines (hence relatively low torque) forces to have aggressive gearing which results poor economy. Great pleasure, sounds amazing, but not efficient...
There are other types of efficiency, not just fuel consumption/mileage economy efficiency.
i.e., HP/liter of displacement.
Also, fuel consumption/mileage economy efficiency has to be taken into context. I don't think S54 / S65 engines' fuel consumption are all that bad, considering they do produce 340 and 420 hp each.