The 2012 Subaru Legacy has the honor of getting the highest fuel economy ratings of any mid-size sedan with all-wheel drive. That's a small group, granted, but it's due to the Lineartronic continuously-variable (CVT) automatic transmission that's available in the Legacy 2.5i model. It's rated at 23 mpg city, 31 mpg highway, and a combined 26 mpg--a figure we've met or exceeded in a mix of driving.
Sadly, though, the rest of the Legacy range doesn't return gas mileage that's so impressive. Opting for the six-speed manual is one hit (it drops to a combined 22 mpg rating), and the more powerful turbocharged 2.5GT engine takes it down further to a combined 21 mpg (and requires premium gasoline as well).
Worst of all, the 3.6R models with the six-cylinder engine and a five-speed automatic come in at 18 mpg city, 25 mpg highway, for a combined rating of 20 mpg--significantly below some competitors' six-cylinder models, though admittedly they may not offer all-wheel drive.