The ML does feel a little more nimble with the gasoline engine, and when the road turns curvy, the seven-speed automatic doesn't work quite as well with the diesel. We noticed a moment of hesitation—enough to lose some momentum—with the BlueTec when going back into the power after slowing for tight corners; and the hesitation seemed related to shift logic more than anything, as commanding a downshift ahead of time with the steering-wheel paddle-shifters completely remedied the situation and made the powertrain feel more responsive.
With either engine, the new M-Class gets significantly better gas mileage. EPA fuel economy ratings are up to 17 mpg city, 22 highway for the gasoline ML350 and 20/25 for the ML350 BlueTec. We saw about 24 mpg with the diesel, over more than 200 miles of mostly highway driving, some of it in excess of most states' speed limits, and in a somewhat lower-speed stint in the gasoline version, we saw a still respectable 21 mpg.
New electromechanical steering doesn't quite have the dead on-center heft that some former M-B systems have had, but that's fine; it's true to the secure and confident feel of the entire vehicle, yet responds quickly when needed and has a variable-ratio rack that's handy for parking. One disappointment is the feel of the brake pedal—just a little vague and spongy, even though the brakes can haul this big ute down from autobahn speeds with total confidence.
Still surely a utility vehicle at heart
With a tow rating of 7,200 pounds, the 2012 M-Class is very capable—especially in torquey BlueTec guise—of getting the jet-skiis out to the lake. And yes, it's still fully capable of off-roading, in all but the most rocky, precarious situations. The 4Matic system's electronic, stability-system-linked 4-ETS torque distribution can send nearly all engine torque to whichever single wheel can use it. The suspension is also remarkably versatile for a combination of on-road use or off-roading—such as the dusty trails we saw out in Montana ranch country—with a so-called stroke-dependent setup that is softer when the surface demands it, firmer otherwise for more body control. Later in the model year, you'll also be able to specify an off-road package with an automatically detaching roll-bar system.
Much-improved aerodynamics—and a spoiler at the back of the roof, as well as more attention to aerodynamics in general, means that you'll rarely feel road fatigue on daylong drives; the M-Class simply feels quieter and more comfortable at triple-digit speeds—which, by the way, sneak up remarkably easy on you with the BlueTec.
For those times when you are yawning (and perhaps weaving) a little too much, Mercedes-Benz has that covered, too. Attention Assist, which takes tabs on driving style to help identify the signs of drowsy driving—triggering a coffee-cup icon and some warning beeps—is now a standard feature on all M-Class models.
Otherwise, you can count on the new sound system (or upgraded Harman/Kardon system) for some varied and superb-sounding entertainment; it includes an SD card slot, 10 GB of audio storage, CD/DVD compatibility, HD radio, weatherband, and Bluetooth audio streaming—as well as Bluetooth hands-free calling. There's also a USB port within the center console.