Two G-Class models are defined by their powertrains. The 2010 G550 sports Mercedes' widely used, smoothly stalwart 382-horsepower V-8 engine coupled to a seven-speed automatic. Cars.com notes that transmission "feels better groomed for [highway driving], downshifting two or three gears at a time for quick, confident bursts of power." The G550 accelerates to 60 mph in about 8 seconds; it also struggles to achieve a 12/15 mpg fuel economy rating.
The 5.5-liter, 500-hp G55 AMG adds an intercooled supercharger and upgrades to a beefier five-speed automatic to push the barn-door body through the atmosphere. The G55 AMG pounces more brutishly to 60 mph in 5.4 seconds, while gulping gas to the tune of 11/13 mpg. Car and Driver states that "a sprint to 62 mph is accomplished in 5.9 seconds and the vehicle tops out at 131 mph. Both figures are impressive, considering the G's massive weight and aerodynamics resembling a concrete wall."
Edmunds says the G55 is "quicker to 60 mph than any other comparable large SUV we've tested."
On-road performance is about what you'd think. The top-heavy feel requires rapt attention on the highway, to control the slow steering and to manage the body through crosswinds. Steering the G-Class requires substantial upper-body strength; "the old-school recirculating-ball steering requires Popeye arm strength and offers limited feedback at higher speeds," says Edmunds. The gas pedal requires a hefty foot, and so does the brake-no multitasking allowed-and Cars.com reports good feel with "full-power braking in panic stops." Still, the amount of ultimate grip available is astonishing, and the G55 model can be hustled to its limits thanks to big, grippy 19-inch wheels and tires and upgraded brakes.
With its tall-wagon handling and decent ride, the appeal of the G-Class clearly rests in its extreme off-road talents. It looks heavy-duty-and it is. An automatic four-wheel-drive system with three electronic locking differentials and low-range gearing keeps it clawing over rocky paths and plugging through muddy bogs where you'll only find Land Rovers and wildlife. Off-road capability is a big selling point for the 2010 Mercedes-Benz G-Class. Edmunds suggests the G-Class is better off pavement than on: "the G exhibits significant body roll, while its front and rear solid-axle suspension is better suited for tackling rugged off-road hills than it is for cruising through Beverly Hills." Car and Driver states that the 2010 Mercedes-Benz G-Class "will go places others can't" and "negotiate the most taxing terrain thanks to solid axles, high ground clearance, and three lockable differentials."