2008 Mercedes-Benz ML320 CDI Review
DRIVING DOWN THE ROAD
WITH CAREY RUSS
2008 Mercedes-Benz ML320 CDI
The question is: how to get decent fuel economy from a capable SUV? A hybrid system, perhaps? Perhaps not - gasoline-electric hybrids are most efficient in low-speed city and commute driving, and a hybrid system, while perfectly adequate for a civilized crossover that will never see more dirt than perhaps the stadium parking lot, is not really meant for real off-road use. So what else would work?
Case in point: on a 400-mile highway trip in the 2008 Mercedes-Benz ML320 CDI that was my test vehicle for the past week, I averaged 24.5 mpg. This was with four people aboard, at speeds up to 75mph (life in the slow lane on California's Highway 5), and in temperatures over 100 degrees F. We had no need for any off-road excursions, but I've had experience in dirt in other MLs, and they work very well there.
Recalibrate your thinking about diesel power. In its newest form, not only is Dr. Diesel's compression-ignition brainchild fuel-efficient and powerful, it's also clean, quiet, and civilized. Because of worldwide emissions and fuel economy requirements, diesels are now undergoing technological evolution comparable in effect to what occurred with spark-ignition engines in the 1970s, but without the mistakes. Advances in materials and electronics mean none of the kludgey devices that destroyed engine performance in the automotive Dark Ages, sometimes with only dubious gains in emissions reduction.
Credit is also due to diesel fuel itself. It's being reformulated in order to reduce emissions, similarly to what happened to gasoline thirty-plus years ago. Analogously to the need for unleaded gasoline for use with a catalytic converter, ultra-low sulfur diesel fuel is required for the oxidation catalyst and particulate filter in the ML320 CDI to work properly. There's more to come, as for 2009 the ML, and Mercedes-Benz's GL- and R-Class SUVs, will get the Bluetec technology currently available only in the E 320 D sedan. This will make them even cleaner, and also 50-state legal. Currently the ML 320 CDI is not available in California-emissions states.
My front-seat passenger was familiar with diesels, being the owner of a Dodge Sprinter van. He didn't realize that the ML was a diesel until the next morning, when he heard it idling from outside. From inside? It's very hard to tell unless you're driving, and then only the low engine revs - averaging just over 2000 - offer a hint. Throttle response is immediate, helped by the 398 lb-ft of torque available from 1400 to 2800 rpm. Towing? Of course - up to 7200 pounds, considerably more than any crossover or hybrid that might get equivalent mileage. The ML diesel has all of the (considerable) comforts and safety features associated with Mercedes-Benz. Drawbacks? Diesel fuel is more expensive than gasoline, although the improved efficiency and mileage of the compression-ignition engine is still better than that difference. And if you may need to look a little harder to find diesel, you'll look less often.
APPEARANCE: Other than badging, the ML 320 CDI looks like any other current Mercedes-Benz ML. Which means that while its shape and proportions are instantly recognizable, being similar to those of the first-generation, the details are very different. It's larger, but not by all that much, and has much more complexly-sculpted and bodywork, especially on the sides. What were gentle curves on the old ML have become more angular and better-defined, and the windshield slopes more, for lower aerodynamic drag. The front styling is even more car-like, with a low, wide perforated grille that displays the Mercedes-Benz tri-star, and is flanked by complex, faired projector-beam headlights. The sides feature large wheel arches and a broad C-pillar that hints at the shape of an S-Class luxury sedan roof line. An upwards-trending character line helps impart a look of motion. At the rear, the signature tail lights have sharp corners, and twin rectangular exhausts hint at performance.
COMFORT: The ML's interior is as highly-styled as its exterior, but form does not sacrifice function or comfort. The increased wheelbase and width of the second-generation ML translates directly to more interior space. Instruments and controls are generally well-placed, but some controls exhibit the quirks for which German cars are famous. In particular, you will mistake the cruise control lever for the turn signal lever at least once, and then there is the electronic "Direct Select" shift lever on the steering column, used for basic P, R, N, and D selection, with manual over-ride by rocker switches on the back of the top steering wheel spokes. Direct Select is a bit strange at first, but you will quickly adapt, and it frees space on the console for extra-large American-spec cupholders. The COMAND system interface, for the audio and navigation systems, has its own learning curve. The CDI comes is well-equipped in standard form, although leather seating and wood trim are options. Driver visibility is good, and the seats allow long drives with minimal fatigue. The climate control system - dual-zone standard, triple (rear controls) optional - is one of the best I've experienced, with cool air almost immediately, even after the car sat parked outside in 90-degree temperatures for a couple of days. The rear seat has room for six-foot adults, and the usual 60/40 split and flip-and-fold-flat cushions and seatback make cargo duty easy.
SAFETY: M-Class passengers are surrounded by a strong central safety cell and front and rear crumple zones. Good four-wheel disc brakes are aided by a four-channel antilock system and Brake Assist. The standard 4ETS four-wheel drive system includes traction control, and the ESP electronic stability enhancement system is standard equipment. Dual-stage front airbags, front and rear side airbags, side-curtain airbags and a roll-over sensor are all standard equipment.
RIDE AND HANDLING: The original M-Class was one of the best-handling SUVs, and Mercedes-Benz has only improved upon that. With a lighter and more rigid unibody chassis structure, and revised fully-independent double wishbone front, multilink rear suspension, it is among the most car-like of SUVs in its ride and handling abilities on the road. The only time it's easy to tell the ML is not a luxury car is over highway expansion joints and other sharp jolts, when the mass of the large wheels and tires (here 255/50 HR 19 on alloy rims) makes its presence known. And even that is subdued compared to many other SUVs. Attention to aerodynamics not only benefits fuel economy, it also results in low levels of wind noise and good stability in strong winds.
PERFORMANCE: Modern diesel vehicles are neither slow nor noisy, and the ML 320 CDI is a fine example. With a 0-60 time of 8 seconds, it won't hold up traffic, and, except for a subdued rattle when cold, it could be just another gasoline-powered SUV. Clouds of soot are absent, thanks to the oxidation catalyst and particulate filter. Construction of the 3.0 liter V6 is little different from a modern gasoline engine, with aluminum alloy dual overhead cam heads with four valves per cylinder and an aluminum alloy block with iron cylinder liners. The variable-nozzle turbocharger and air-to-air intercooler could also be used in a gasoline engine. But a 16.5:1 compression ratio and high-pressure (22,700 psi!) common-rail fuel injection with piezo-ceramic fuel injectors are high tech, diesel style. Ceramic glow plugs are used for starting in cold weather; with temperatures never below 70 even at night during my time with it, the CDI started as quickly as any modern gasoline vehicle. If the horsepower rating of 215 at 3800 rpm doesn't seem any better than an older naturally-aspirated 3.0-liter V6, the 398 lb-ft of torque available from 1400 through 2800 rpm provide strong acceleration and towing ability. EPA mileage is 18/24, and if I believe the trip computer, I got around 20 in town and over 24 at a steady 70 or so on the open road. Passengers may want to stop before the ML needs to. The seven-speed automatic transmission uses adaptive logic to "learn" the driver's style and shift accordingly, and works perfectly well in D. Also, the transmission has multiple shift modes, for use in off-road and when towing. The full-time four-wheel drive system splits torque 50/50 front/rear in normal operation, with more going to the axle that can best use it, and wheel control via the ESP logic and engine and individual brake modulation.
CONCLUSIONS: With clean diesel power, an off-road capable SUV can be fuel-efficient and civilized. Best example yet: the 2008 Mercedes-Benz ML320 CDI.
2008 Mercedes-Benz ML 320 CDI
Base Price $ 44,650 Price As Tested $ 60,860 Engine Type turbocharged and intercooled dual overhead cam 24-valve aluminum alloy 72-degree diesel V6 with balance shaft and common-rail direct fuel injection Engine Size 3.0 liters / 182 cu. in. Horsepower 215 @ 3800 rpm Torque (lb-ft) 398 @ 1400-2800 rpm Transmission 7-speed automatic Wheelbase / Length 114.7 in. / 188.5 in. Curb Weight 4,817 lbs. Pounds Per Horsepower 22.4 Fuel Capacity n/a gal. Fuel Requirement ultra-low sulfur diesel fuel Tires 255/50 R19 107H Michelin Brakes, front/rear vented disc / solid disc, ABS, BAS, ESP standard Suspension, front/rear independent double wishbone / independent multilink Ground clearance 8.3 inches Drivetrain in-line front engine, single-range 4-wheel drive PERFORMANCE EPA Fuel Economy - miles per gallon city / highway / observed 18 / 24 / 24 0 to 60 mph 8.0 sec Towing capacity 7200 lbs. OPTIONS AND CHARGES Parktronic $ 770 Rear seat entertainment system $2,670 Heated front seats $ 710 Premium III Package - includes: Adaptive Damping System, rearview camera, power passenger seat with memory, autodimming mirror, power driver's seat and steering column with memory, rain-sensor wipers, hands-free communication system, power steering column, air suspension, power folding mirrors, rear audio controls, DVD navigation, Sirius satellite radio, 3-zone climate control, infrared glass, headlamp washing system, bi-xenon curve illumination headlamps, corner illumination front foglamps, Harmon/Kardon sound system, power liftgate, cargo organizer system $8,600 Leather Seating Surfaces Package - includes: leather seating surfaces, wood and leather steering wheel, burl walnut trim, interior ambient light package $1,975 Destination and delivery $ 775