OK, taking a purely logic (i.e. engineering) stab at this: 
Why does the 2014 Forester rate +2 mpg with basically the same setup:  2.5L Boxer, CVT, AWD??? 
Logic would say the Forester would get worse, since it's more aerodynamic inefficient (taller, less sleek). 
The Imprezza/Crosstrek do better due to smaller engine (2.0L Boxer) so that I can understand (as well as being smaller vehicles). 
But I don't get why the Forester/Outback are so different in Highway MPG here.  
Anybody know the answer to this? 
TIA