Many test drives, have shown it has home in 2nd place after the Nissan Altima, but ahead of the Honda Accord. I would assume the Mazda6 would win, if it used the a CVT like the Accord and Altima.
I think the point is that Mazda touts their technology as 'amazing' and a total re-invent of the internal combustion engine and its associated mechanicals...but Subaru, Nissan, Honda, etc. are showing that a proper transmission can do far more for fuel economy than the entire "SkyActiv" treatment. Just think what a SkyActiv CVT could do...
Don't get me wrong - I'm ALL for SkyActiv - I think reducing weight, friction, and drivetrain losses are the ideal!!! I just think that it's something of an oxymoron to try to get the best efficiency from extant technology, and then use a less-efficient transmission.
The problem is that Mazda's touting SkyActiv as an alternative to using hybrids - it's an advertising game. To keep the "fun to drive" they won't use a CVT, but in the real world, a proper CVT is the efficient way to go, even if auto enthusiasts don't like them.
Just look at Subaru with the new Forester - same FB25 engine, vehicle actually got heavier (~50lbs), yet it now gets 5MPG better on the highway (thanks to a reduced cd to 0.33) and 3MPG better in the city with the only change being the introduction of a CVT over the 4EAT.
My $0.02. I think Mazda's done an amazing job, but to truly beat the fuel economy game, they should at the very least consider a CVT - maybe with PROPER pre-set ratios to simulate a traditional automatic (a la Subaru S.I. Drive) to maintain the driving fun.