German Car Zone

With Bluetec diesel variants of its luxury SUVs available, Mercedes-Benz says diesels are now environmentally as clean as gasoline engines, while providing the big torque Americans love, with greater fuel economy than comparable gasoline-fueled SUVs. After sampling the latest Bluetec 320 ML, GL and R models, we're believers.

All models share the 3.0-liter diesel and seven-speed automatic combination. For '09, AdBlue--an aqueous urea solution in an onboard 28- to 32-liter tank--is injected into treated exhaust gas, which runs through a converter, reducing nitrous oxides into harmless nitrogen and water. The AdBlue tank is replenished as part of regular servicing. Mercedes is the first manufacturer to register 50-state diesel SUVs.

The only "diesel" clues are discreet Bluetec badges on front fenders and rear hatches. When you push the ML320's start button, there's no shudder, vibration or clatter. Engineers paid particular attention to controlling high-pressure injection-system noise and isolating vibration with body and engine bearing mounts.

These vehicles make big torque, 398 lb-ft holding between 1600 and 2400 rpm. The engine is rated at 210 hp at 3800 rpm, and with the tachometer dial marked in widely spaced 200-rpm increments, each marker carries big weight.

Accelerating hard from rest, there's instantaneous, locomotive-like push. Power flows smoothly, effortlessly and quietly. Full-throttle upshifts, also smooth, happen at 4000 rpm indicated; if you're paddle-shifting, the tranny shifts itself before it lets you overrev. Indicated rpm at speeds of 40, 50, 70, 80 and 100 mph are 1400, 1600, 2100, 2650 and 3000, respectively. Midrange acceleration is strong at 50 to 70 mph and 80 to 100 mph.

Four-wheel-drive systems carry over, and the Bluetec powertrain qualities were the same for ML, GL or R--dip your toe into torque at any time. An '09 5.4-liter-V8 gasoline ML550 model makes more horsepower (382 at 6000 rpm) yet less torque (391 lb-ft at 2800 to 4800 rpm). The driving experience in the gasoline model was busier, and the power was more explosive and higher up than with Bluetec, which was more relaxed in nature, in some ways more refined. Midrange acceleration was quicker in the gasoline model. Mercedes estimates that the gasoline model goes from 0 to 60 mph in 5.6 seconds and returns 13 mpg city and 18 mpg highway, versus an ML320 Bluetec's 8.0-second 0-to-60 and 18/24 mpg. We saw 22.5 mpg with a heavy throttle foot.

Bluetec adds 200 pounds, yet these substantial vehicles still handle "smaller" than they are, surprisingly agile, with very little roll and great curve appeal.

All models get a leather multifunction steering wheel, controlling navigation readouts, in-dash computer, cell phone and more. A new tele-matics system offers hands-free Bluetooth, media interface and voice command. The ML gets more changes, with more supportive front seats and new styling of front and rear bumpers, headlights, grille and mirrors. All models get new wheels. Accident sensing is standard, with active head restraints.

Prices aren't set; expect a premium of $1,000 over gasoline-engined models.



SPECS
ON SALE: October
BASE PRICE: ML/GL/R
$46,075/$54,475/$46,675 (est)
DRIVETRAIN: 3.0-liter, 210-hp, 398-lb-ft V6 turbodiesel; awd, seven-speed automatic
CURB WEIGHT: ML/GL/R
4974/5313/5092 lb
0-60 MPH: ML/GL/R
8.0/9.1/8.6 sec (mfr)
FUEL ECONOMY (EPA): ML/GL/R
20/19/20 mpg



DRIVES: 2009 Mercedes-Benz Bluetec ML 320, GL 320, R320 - AutoWeek Magazine


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