The M-Class SUV might be the Swiss Army Knife in the Mercedes-Benz lineup. It isn't so large that it's cumbersome or hard to park, but it comfortably seats five and carries plenty of stuff. As daily transportation, it doesn't feel like a truck, and it won't beat its driver or passengers up. Yet it has the potential for some fairly serious off-road adventuring, and it can tow up to 5,000 pounds. The M-Class is more than powerful enough in any of its variations, with the safety equipment, luxury accoutrements, style and smooth finish expected of a Mercedes-Benz.

For 2007, the M-Class line features two new, very different models that will further broaden its appeal: The fuel-efficient ML320 CDI diesel and the ultra-high performance ML63 AMG.

With the ML320 CDI, you can forget just about everything bad you knew about diesels. It gives up nothing to the standard, gasoline-powered ML350. It's equipped identically, except for its diesel engine. The 3.2-liter diesel V6 generates 398 pound-feet of torque, comparable to a large-displacement V8, and brings a substantial improvement in fuel economy.

The ML63 AMG features a hand-built V8 that generates 503 horsepower with AMG tuning and enhancements to match all that power. Though considerably more expensive than other M-Class models, the ML63 AMG is a true high-performance machine. Its 6.2-liter V8 is hand-built by a single technician. It bursts from 0 to 60 mph in 4.8 seconds, according to Mercedes, with top speed electronically limited at 155 mph. Plus, it comes with the full load of luxury features.

The original M-Class helped make luxury SUVs a familiar part of the automotive landscape. Completely redesigned for the 2006 model year, this second-generation M-Class is better than the original in every way. It's roomier, more comfortable and more car-like in its bearing. Its wheelbase is almost four inches longer, and its body three inches wider, all to better accommodate larger Americans inside. In the bargain, the coefficient of drag, or Cd number, has dropped from brick-grade to a sylphlike 0.34, on par with many passenger cars that are much lower to the ground. This means quieter highway travel and better fuel economy.

In place of the original body-on-frame, truck-style design, this latest-generation M-Class has welded unibody construction with isolated front and rear subframes, a technique that emphasizes rigidity, decreased vibration and lower weight. The unibody also reduces its overall height, making it easier for families to get in and out. The M-Class has given up any pretense to being a large-family vehicle. The optional side-facing rear seats from the old model are gone (they weren't very good anyway), so the M-Class is strictly a five-seater. You'll want to look at the GL-Class for seven-seat SUV accommodations.

The new look and larger size come with a new double-wishbone front suspension and four-link independent rear suspension, emphasizing sedan-style dynamics. Yet with a two-range transfer case on most models, and a sophisticated control program for the fulltime all-wheel-drive, the M-Class can get its driver through some fairly tricky off-road situations.

M-Class buyers will pay a premium over many other comparably equipped luxury SUVs, but those who appreciate the cache and engineering strengths of the Mercedes brand will find plenty to like here.

New for 2007 are three significant options: A dual-screen rear-seat DVD entertainment system, a rearview camera that shows the area behind the vehicle when reverse is engaged, and a Bluetooth interface for cell phones that provides integrated, hands-free operation without docking the handset.