Mercedes-Benz of Naples

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Driving Impressions

The Mercedes M-Class models will do just about anything most owners demand, on road or off road. Acceleration performance varies across the model line, ranging from better than adequate in the ML320 BlueTEC and ML350 to race-like with the ML63 AMG. Ride quality on pavement is never rough, even in the more stiffly suspended ML63, which features the Airmatic air suspension as standard equipment.

The BlueTEC diesel boasts more torque than the ML550's hefty V8: 398 pound-feet, at 1600-2400 rpm; vs. 391 at 2800-4800. And it's torque, not horsepower, that gets you going and pulls trailers up hills. (Properly equipped, the BlueTEC tows the same 7,200 pounds as the ML550.)

BlueTEC delivers better fuel economy than any other M-Class model, with an EPA estimated 18 mpg city/24 mpg highway. With a 25.1-gallon tank that means a cruising range of 600 miles. For comparison, the gasoline-V6 ML350 rates 15/20 mpg city/highway (with 2WD or 4WD); the ML550, 13/18; the ML63 AMG 11/15.

Mercedes reports near-identical 0-60 mph times of 8.0 and 7.9 seconds, respectively, for the ML320 BlueTEC diesel and the ML350 gasoline V6. Yet that doesn't tell the whole story, because even last year's diesel's whopping 398 pound-feet of torque (compared with 258 pound-feet for the ML350) came across as a neck-whipping burst of acceleration. And of course turbocharging maintains power in high-altitude environs. And for this the diesel buyer gets a substantial fuel economy improvement in real-world driving. We're perfectly happy in the ML350, but if diesel fuel were readily available on our appointed rounds, we would choose the ML320 BlueTEC over the ML350.

The ML550 is more fun to drive. The 5.5-liter V8 engine will take this 2.5-ton SUV from 0-60 mph in 5.6 seconds, and then settles down to a background burble by the time you reach seventh-gear overdrive. The seven-speed automatic offers a manual-shift mode, and it's the best automatic Mercedes has built. It's flexible, in that it kicks down to a lower gear more quickly than its predecessors, and it almost always keeps the engine in the most productive part of its power band. Yet its overdrive top gear makes for quiet high-speed cruising and better fuel economy.

During several days of hard driving in mountainous, sinuous terrain, we found the ML550 a hoot. The suspension is good at minimizing body roll in high-speed corners, and it smoothes dips and potholes well. The optional Airmatic suspension we tested can be downright supple, which trucks aren't supposed to be. The standard 19-inch wheels and tires and the power rack-and-pinion steering deliver a nice feel of the road, and quick reactions when necessary. At high speeds through mountain passes, the ML550 leans over a little, takes a set, and then grabs the ground and turns the corners.

Critics have complained with some justification about the electronically actuated and modulated Sensotronic brake system that Mercedes-Benz has been feeding gradually into all of its models over the last few years. We're getting used to them, and they'll stop the M-Class right now without much pedal effort. They've also improved considerably since they were first introduced. Yet they still don't have the smooth, linear feel of the best mechanically actuated brake systems. Nice smooth stops can be tricky without practice. We prefer the brakes in the Mercedes cars that do not have Sensotronic.

Off road, the M-Class offers the advantages of two significant features: a Downhill Speed Regulation software control that maintains the 4-12 mph downhill pace you set through the wheel controls, and a Start-Off Assist that keeps the vehicle from drifting backward in Drive or forward in Reverse on steep hills. Very handy, indeed, and easy to learn to use.

All M-Class models are rated at a significant 7,200-pound towing capacity with the optional Class III towing package, but note the tongue weight rating may be the limiting factor. We have little doubt that three of the five, including the BlueTEC diesel, would be up for the job. (The diesel generates as much torque as a large displacement V8.) We'd have some doubts about the gasoline V6 in the ML350, however. If towing a substantial load were a regular part of our routine, we'd look at the ML320 BlueTEC or the ML550.

We've driven the ML63 AMG and it certainly has appeal: a people hauler to do battle with Porsche 911s in the stoplight derby or blast through big sweeping curves much faster than decorum or good sense might suggest. The ML63 is fast, dashing from 0 to 60 mph in less than five seconds, and, with the torque of a large V8 and the high-revving character of a sports car engine, it can be fun to drive. But it's also big and heavy, so don't think sports car. Through the twisties where we sampled it, changing directions quickly and often, the ML63 AMG is not exactly fun. Its massive tires mean plenty of grip. The steering is fairly quick for such a hefty machine, but also quite light, and the package conspires to feel twitchy, almost unsettling.

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