Both gas-engine models accelerate briskly, though the ML500's V8 delivers more thrust in all conditions. However, the transmission is compelled to upshift and downshift more frequently in the ML350, versus the ML500, in response to throttle inputs. In two test ML350s, the transmission periodically suffered jerky gear changes at low speeds. The ML320 CDI suffers slight delay in power delivery from a stop, or brief turbo lag, but then accelerates briskly. Fuel economy is about as expected. A test ML350 averaged 17 to 19 mpg. Gas-engine MLs require premium-grade fuel, while the turbodiesel in the ML320 CDI needs low-sulfur diesel fuel. CDI models are not sold in California or certain Northeastern states. Expect low-speed impact harshness over sharp bumps and ridges. Otherwise, these SUVs ride with admirable comfort and are rewardingly composed. Mercedes' available air suspension has Comfort, Sport, and Automatic settings. In Sport setting, the ride gets uncomfortably choppy, but other modes have little evident effect on comfort or control. Steering is impressively linear and accurate, though some drivers may prefer lighter low-speed feel. An M-Class corners with impressive grip and balance, and no excess body lean. These Mercedes models act more like tall station wagons than SUVs, but they do lean more in corners than the sportier Acura MDX, BMW X5, or Porsche Cayenne. Strong stopping power is matched by outstanding brake-pedal modulation. Quietness is another virtue, with luxury-car levels of road- and wind-noise suppression. The V6 is heard more than the V8, by virtue of more-frequent shifts. Otherwise, it's no less refined in sound and feel than the silken V8. The ML320 CDI's turbodiesel makes a slightly different noise than gas engines, but is not much louder overall. Dashboards present an upscale blend of businesslike gauges and sophisticated but easy-to-use controls. Large, well-marked climate dials deserve special praise. Gear shifting via the short column lever takes some practice. The lever falls easily to hand, but returns to the same position after each shift, requiring the driver to monitor gear selection as indicated on the instrument panel screen. Mercedes' navigation system absorbs most audio functions, and requires multiple steps for some basic tasks. Test models had leather/wood cabin trim. Materials are notably rich in feel and quality, for upscale ambience, though most panels are firm rather than soft to the touch. Roomy front seats are supportive in cruising and cornering, though the Comfort Package's 10-way seats have a tacked-on control pod that can intrude on leg space and looks incongruous. Entry/exit is easy via large doors and no-stress step-in height. Rear occupants enjoy good leg, foot, and headroom on a nicely contoured seat, which fits three-across with only minor crowding. Narrow lower doorways slightly impair entry/exit for the rear compartment. The tall, broad cargo bay offers plenty of space even with rear seats in use. Rear seat cushions tip, and seatbacks fold easily without removing headrests to create a long, flat load floor. Good cabin storage includes roomy door pockets, a tiered console bin, and wide space where the floor shifter was previously located.

Value for the Money
Around-town ride comfort isn't quite up to par. Overall, though, the highly refined, rock-solid, and engaging-to-drive M-Class is what a premium midsize five-passenger SUV ought to be. New-car base prices have been very competitive, but could grow daunting as options are added. Fairly strong resale value tends to keep secondhand prices on the high side, though AMG models depreciate faster.