The diesel engine option that we thought would show up in the Mazda 6 (and allow it to top 40 mpg) isn't arriving for 2014. That said, the 2014 Mazda 6 is a very fuel-efficient car with its base four-cylinder gasoline engine—incorporating a suite of so-called SkyActiv technologies that include direct injection, variable valve control, and a very high 14:1 compression ratio.
Based on what we've seen with both this 2.5-liter version in the Mazda6, as well as the smaller 2.0-liter version that's going in the Mazda3, this engine delivers excellent real-world mileage—perhaps 3 to 5 mpg better in real-world driving than other vehicles that have comparable EPA ratings. Like many cars in its class, the Mazda6 now does better with the automatic than with the manual in the official test as well as in real conditions—mostly because the automatic is so good at quickly bringing engine revs down when they're not needed.
In brisk driving, over 125 miles of suburban boulevards and country two-laners, mostly, with some expressway driving, we averaged nearly 31 mpg in an automatic Mazda6.
Add the GT Technology Package, and you get the capacitor-based i-ELOOP system, earning 2 mpg better in both the city and highway cycles—for a net 28 mpg city, 40 mpg highway--32-mpg Combined in a mid-size sedan; no clunky hybrid battery pack. This brings a phenomenal 656-mile highway range.