Well, this Ecoboost is the one intended to replace a V8, so the mileage is better than that would have, but it's still a 350HP engine with 350lb/ft of torque. So we get about 11/20. There is no V8 offered in the Flex.
I guess Chevy's version for saving fuel is their multi-displacement system (Dodge/Chrysler has a similar system) whereby it shuts down 4 cylinders under light load conditions - typically <55 mph on flat roads just cruising. With that our suburban get a similar 11/20 as well.
My focus ST has 250 HP - too fun to resist. I just wish the boost gauge showed negative pressure in addition to positive.
I'm really liking the whole Ford Ecoboost platform - all the vehicles I've rented with it performed really well and got pretty good gas mileage if you took it easy.
ymmv - really