2013 Chevy Malibu - ECO model gets 38 MPG!

[Kal-El]

Originally Posted by why?

eww i think that is gross. I just wonder though how slow these cars are, what else can they do but manipulate the transmissions to test out at these numbers?

GM does a lot more than simply put a tall 6th gear in the ECO models.
Using the Cruze Eco as an example, here's an excerpt from an article that talks about some of these changes...

So what has GM actually done to its pint-sized sedan to be able to wring out such lofty fuel economy claims? The company says that it tackled the Cruze Eco with a three-pronged strategy to maximize the vehicle's efficiency. That started with optimizing the vehicles aerodynamics, but carried into reducing weight and tweaking the powertrain a bit as well.

On the aerodynamic front, GM bolted on a complete underbody tray to reduce wind turbulence, and small plastic spats were installed ahead of each tire to better control airflow around the wheels. Additionally, the engineers made the decision to reduce the Eco's tow rating (yes, the Cruze has a tow rating), allowing them to further close off the front grille while still maintaining proper engine temperature.

But the biggest aerodynamic claim to fame comes from the Cruze Eco's trick active shutter system. Once the vehicle reaches a speed of around 38 mph, an algorithm calculates input on everything from ambient air temperature to engine temperature and load to determine when to automatically close a set of plastic slats nestled in the lower fascia. All told, the aero tweaks netted the Cruze Eco a coefficient of drag that's 10 percent slipperier than that of the standard sedan.

GM also set about stripping as much weight as possible from the four-door, starting with a set of special Alcoa forged-aluminum 17-inch wheels that are 5.3-pounds lighter per wheel than the stock rollers. In fact, The General's engineers are fond of saying that no piece of sheetmetal went unweighed in the quest to slim the Cruze Eco's waistline. A total of 42 changes were made to the car in the name of shedding pounds, and as a result, the green-leaning Cruze hits the scales at a relatively feathery 3,009 pounds. That's 214 pounds lighter than the standard-issue model thanks to things like smaller weld flanges throughout the structure and thinner sheetmetal on a few body components.

Pop the hood and a host of mechanical changes join in the fight to help the Cruze Eco nab its lofty EPA numbers, too. While one of the most obvious changes is that the 1.4-liter, turbocharged four-cylinder engine is bolted to a six-speed manual gearbox, the minds at GM have pulled a few other quick tricks to squeeze as much efficiency as possible from the recipe. The air-conditioner compressor now wears a clutch in addition to being continuously variable to reduce drag on the engine. Likewise, an intelligent charging system only engages the alternator when it's required.