The 2008-model M-Class marks the debut of the V8-powered ML550, which replaces the earlier-architecture ML500. The new ML550 has a higher level of performance, wîth a 5.5-liter V8 engine wîth 382 hp and 391 lb-ft. of torque. This vehicle also stands apart wîth its standard sunroof, exclusive AMG styling, 19-inch AMG wheels and running boards for a perfect combination of styling and performance.

Other M-Class models include the popular ML350 (powered by a 3.5-liter, four-valve-per-cylinder V6 engine delivering 268 horsepower and 258 pound-feet of torque), the recently introduced ML320 CDI (which comes wîth a fuel-sipping, high-technology CDI diesel that provides the pulling power of a V8 and the fuel economy of a four-cylinder) and the flagship of the M-Class line – the high-performance ML63 AMG, which features a 6.3-liter, AMG-designed V8 that produces 503 horsepower and 465 lb.-ft. of torque.

Price: $44,000 – 87,000.
Invoice: $40,920 – 80,910.

EXTERIOR

The M-Class makes a bold statement wîth the aggressive wedge shape of its exterior styling, which is complemented by sweeping front fenders, dramatic shoulder lines and a sharply angled windshield. Widely flared rear wheel arches and a horizontal body line work in concert wîth an angled ‘C-pillar’ to emphasize a sense of forward motion. The athletic design theme is reinforced by the dynamic appearance of the front grille, which features three wide louvers wîth pronounced air vents complemented by the chrome Mercedes-Benz star. Strong horizontal lines on the grille also emphasize the sport utility’s wide stance. Two ventilation grilles on the hood incorporate the signature three fins found on many classic and contemporary Mercedes-Benz cars, and help to underline the dynamic qualities of the new M-Class.

Viewed from the rear, wide track and flared rear wheel arches continue the muscular design theme, while twin tailpipes and a prominent rear spoiler provide a strong visual reminder of the new model’s performance potential. For 2008, the new V8-powered ML550 wears AMG body styling, which includes deeper front and rear under-bumper aprons, as well as 19-inch AMG wheels and running boards. The ML63 AMG continues unchanged, and its equipment includes AMG body styling and 20-inch wheels and tires. All M-Class models come wîth a power glass sunroof as new standard equipment for 2008. The ML350 and ML320 CDI models also get 19-inch alloy wheels, a silver painted and chrome grill wîth matching exterior trim and blue-tinted glass.

The front-end styling is accentuated by eye-catching projector-beam headlights, comprised of three individual chrome tubes. Optional Bi-Xenon curve-illuminating headlights combined wîth corner-illuminating front fog lights provide enhanced visibility. These swiveling headlights follow the §teering input of the driver to rapidly pivot to the relevant side when the car enters a bend, improving road illumination by up to 90 percent over fixed lights in turns. When the driver activates the turn signal or turns the §teering wheel (below 25 mph), the corner illuminating fog lights illuminate areas of the road that would remain dark wîth conventional lighting systems – areas that could include a pedestrian or cyclist.

INTERIOR

The interior of the latest M-Class features high-quality materials finished wîth craftsman-like attention to detail. Once inside, the driver is greeted by a four-spoke multifunction §teering wheel wîth brushed aluminum accents on the lower spokes. Behind the §teering wheel is a new Mercedes-Benz electronically controlled gear selector mounted on the §teering column to control the standard seven-speed automatic transmission. A sport-oriented instrument panel is horizontally divided into an upper and lower section in both form and color. Four round circular vents are positioned at the left center and right sections of the sweeping dash, their chrome surrounds reminiscent of the engine housings found on jet aircraft. The upper section of the dashboard arches over the instrument cluster, which is dominated by angled tubular gauge binnacles containing the speedometer and tachometer as well as fuel gauge and clock.

The clearly arranged center console features easily accessible and well-positioned ergonomic controls and displays. Located just below the two central air vents is the standard Thermatic dual-zone climate control and a second-generation MCS II entertainment head unit (or optional COMAND system) that incorporates a single CD slot. Audiofiles will appreciate the optional harmon/kardon Logic 7 audio system wîth an auxiliary input for MP3 players. An optional integration kit allows an iPod to be played through the vehicle’s audio system. When the iPod connects to the car in the glove box, selections can be made from the §teering-wheel controls, and the playlist or titles appear in the central dash display.

The iPod battery is also charged whenever it’s docked. The center console extends gracefully around the center transmission tunnel, which includes two large cupholders wîth the ability to hold two 32-oz. cups or one 44-oz. cup. Two integrated grab handles on the console echo the sweeping lines of the exterior and provide a firm gripping point for those occasional ventures on rough roads. The two-tone color scheme of the interior is repeated on the center console, transmission tunnel and door panels, accented by burl walnut or aluminum trim (depending on the option package).

The door panels are concave in form at elbow level, increasing elbow room, while their contours add a unique element of style. The passenger compartment can accommodate five adults, and the 60:40 split second row is easy to fold when the need arises. While onlookers can admire the M-Class from the outside, passengers will appreciate the spaciousness of all five seating positions. In fact, the distance between the front and rear seat is increased by more than ½ inch (15 mm), achieving a level of comfort more often found in luxury sedans. Knee room is increased by nearly 1½ inches (35 mm) and elbow room by over an inch (32 mm).

ENGINE

The ML350 is powered by a 3.5-liter twin-cam V6 engine that produces 268 horsepower and 258 lb.-ft. of torque. Variable intake and exhaust valve timing requires separate camshafts for the intake and exhaust valves, and valve timing is automatically adjusted within a range of 40 degrees using electro-hydraulic vane-type adjusters. At part throttle, the valve timing adjuster keeps the exhaust valves open as the intake valves are opening, using this valve overlap for internal exhaust gas recircula-tion, reducing exhaust emissions and improving fuel economy. However, approaching full throttle, the camshaft adjustment optimizes valve timing for maximum power. To minimize interfering wîth air flow through the ports, valve stems are only six millimeters or about ¼ inch in diameter (most valves have 8 or 10 mm stems), and the valves are angled at 28.5 degrees to optimize the combustion chamber shape.

That 258 foot-pounds of torque is on tap all from 2,400 rpm all the way up to 5,000 rpm. In fact, at just 1,500 rpm, the new V6 develops 87 percent of its maximum torque! While the variable valve timing system gets a lot of credit for the engine’s unusually broad torque curve, a two-stage intake manifold plays a key role as well. The intake manifold is made of a lightweight magnesium alloy. At relatively low engine speeds, a set of flaps in the manifold close off short intake passages, forcing intake air to take a much longer route into the engine. This creates pressure waves that help the intake process and improve torque at lower engine speeds. Above about 3,500 rpm, the flaps open, and intake air flows the shortest distance to the combustion chambers, helping to generate maximum horsepower, especially at higher speeds.

The ML350 engine is equipped wîth cleverly designed tumble flaps in the intake passages near the combustion chamber. The tumble flaps pivot open under partial load, improving combustion by creating additional turbulence around the intake valve and in the combustion chamber. During higher engine loads such as full throttle, the tumble flaps are completely recessed in the wall of the intake manifold. While better combustion helps improve engine torque, the primary purpose of the tumble flaps is to further increase fuel economy, and tests show that the tumble flaps indeed boost fuel mileage by about two percent.

First, a forged crankshaft wîth four main bearings is placed into an aluminum engine block that features wide main-bearing saddles and transverse bearing supports that minimize vibration. A balance shaft is installed in the block between the two cylinder banks, about where the camshaft is located on a pushrod-type ‘V’ engine. The balance shaft is driven from the crankshaft by a long double chain that loops around one camshaft in each cylinder head and engages the underside of the balance shaft sprocket. This means the balance shaft counter-rotates at crankshaft speed, and its ‘lobes’ cancel out the inherent imbalance and vibration of a 90-degree V6.

The aluminum engine block is cast around Silitek cylinder liners that provide a long-life, low-friction silicon-aluminum running surface for the piston rings. In addition, the block is nearly seven pounds lighter than one wîth conventional cylinder sleeves. Aluminum pistons are pinned onto forged steel connecting rods that are about 20 percent lighter than on comparable engines. The pistons slide into the cylinders, and the connecting rods are clamped around the crankshaft journals. The two cylinder heads are bolted onto the block, and twin camshafts are installed in each cylinder head. The intake camshafts are driven by a double chain, and gears on the intake cams drive the exhaust camshafts.

TRANSMISSION

The M-Class comes wîth the world’s only production seven-speed automatic transmission. When compared to the previous transmission generation, the seven-speed makes the SÚV both faster and more economical while providing smooth, barely noticeable gearshifts. Seven gear ratios provide a wider spread of ratios between first gear and top gear and, at the same time, allow smaller increases in engine speed as the vehicle accelerates through the gears. This gives the electronic control unit more flexibility in terms of maximizing fuel economy and making the transmission’s reaction time extremely fast.

Únlike most transmissions, the seven-speed transmission will skip up to three gear ratios if necessary when it downshifts, shifting directly from seventh to fifth, for example, or even sixth to second. This helps the transmission choose the perfect gear ratio for quick acceleration and ensure almost imperceptible shifts in the process. The Mercedes-Benz seven-speed uses a refined, proven hydrody­namic torque converter wîth a special lock-up clutch inside the converter for maximum fuel efficien­cy. The lockup clutch eliminates the usual torque converter ‘slippage,’ providing the direct connection and fuel efficiency of a manual transmission when the lockup clutch is engaged. In the seven-speed, the lockup clutch engages in all seven gears. (To put that into perspective, many cars lock up the converter only in top gear.) The Mercedes-Benz lock-up clutch is submerged in transmis­sion oil and uses special long-life friction materials.

BODY

The Mercedes engineers who undertook the design of the second-generation M-Class re-examined and analyzed every component – nothing remained sacred. One of the most dramatic departures from the original design is its structural frame. Instead of a separate ‘ladder-type’ frame and body shell, the current M-Class features a self-supporting unit body platform. To handle the high load forces involved in off-road driving, the high-stress points between the suspension and body have been redesigned and – above all – made stronger.

One indication of the result is the body’s higher torsional rigidity, which is now measured at 2.18 mm per meter – significantly better than its predecessor. As a result, the M-Class boasts improved vibration comfort and excellent handling stability. A continuous ‘D-ring’ roof structure contributes to the body’s outstanding rigidity. This robust connection from the floor, sidewalls and roof frame is also used to attach the rear liftgate. In comparison to its predecessor, the M-Class body is about 6 inches longer, nearly three inches wider and about ¼ inch lower. The wheelbase is nearly four inches longer, and there’s 2 ¼ inches more rear overhang.