If anybody is interested in the real world mileage results, I just did a 650 mile trip with a large roof box on my c-max. I'm running the Thule aero-bars with a Yakima SkyBox Pro, it is a pretty big box, the combo is taller than a Ford Expedition. I had a good 150 lbs in the roof box and four people and a full trunk. The trip was 50/50 highway (68 on cruise) and hilly rural two-lane (55-65) through the Adirondack park. Regular old corn-gas in the tank. Temps in the high 80's with the occasional massive thunderstorm added in for good measure. According to the car, the average for the trip was 38.7mpg - I'm pretty happy with that! This was my first drive in the car after the 3.51 update, the GPS is improved a little from a usability standpoint, but still not as good as GPS's I've had in other cars. Bluetooth stuff is improved a little, but bluetooth audio for music from my phone is still rather unpredictable and annoying. Same with iPod integration, it drives me nuts when it goes back to the beginning of an 8 hour book.