True. But the design of trucks is so dreadfully bad in the first place, I can't imagine something streamlining the back end, not making the vehicle more efficient, even a bunch of mini-turbines.
But as I think I implied in my previous post, simply making the vehicle more aerodynamic is much more economical. And I should probably add now, that it is the only logical solution.
The article associated with the image of the truck I posted, stated that the gas mileage went from 25 to 32 mpg @ 70 mph, a 28% improvement. I agree with you that a slew of mini-me turbines, strategically placed, would probably not come close to generating such an improvement.