Scott and hone.
That might be true in the future. But I would think any improvements in efficiency and weight loss is going to apply to both the 2.7 and the 3.5.
Improvements in efficiency can't change the fundamental laws of physics. At one hundred percent efficiency a gallon of gas will only drive the f 150 so far. And It may be that 3.5 liters may be the sweet spot.
A steel body 3.5 is just 1 mpg behind the aluminum 2.7. If the aluminum body does indeed save the mpg claimed. Comparing the numbers, it looks as if the 2.7 is not as good a value as the 3.5.
