The gasoline-powered ML 350 is about par for the class, at an EPA-rated 17 mpg city, 22 highway. But it pretty much goes downhill from there. Opt for the more exclusive ML 550, and fuel economy ratings plummet to 15/20 mpg. And go for performance with the ML 63 AMG, and you'll see 14/18 mpg on the window sticker.
If you want to think green, yet get an off-road or towing-capable luxury SUV that doesn't feel compromised in any way, choose the 2014 Mercedes-Benz ML 350 BlueTEC; you'll get EPA fuel economy ratings of 20 mpg city, 27 highway, which enables a driving range of about 650 miles. It's already our pick of the two V-6 models, but its green credentials make it more of a no-brainer, despite the ML 350's much-improved refinement.