With all the buzz about climbing fuel prices, and how current buyers are looking for new ways to increase their efficiency, it looks like Mercedes-Benz may have found a way to give its SUV buyers the best of both worlds. The second-generation M-Class came out in 2005 and was considered a bit heavy for its size. The smallest engine offered at that point was the all-alloy 3.7L V-6, rated at 15 mpg in the city, and 18 mpg on the highway. 2009 models will do a bit better than that, offering several choices.
The new, freshened M-Class will be offered with a 3.5L V-6 (with fuel economy at 15/20 mpg), a 5.5L V-8 (13/18 mpg), an AMG 6.2L V-8 (11/14 mpg), and the newest, and most impressive of the engine choices, a 3.0L V-6 turbocharged diesel, with an estimated fuel economy of 19 mpg in the city, and (we're guessing) at least 25 mpg on the highway. Although the new ML has several new improvements and styling changes, it's the newest BlueTEC engine and after treatment exhaust system that will shine the brightest.
The newest generation of BlueTEC, currently in all three of the M-B's SUV and crossover models (the R-Class, ML, and GL), uses an aluminum 3.0L V-6 engine with a variable-vane turbocharger, sophisticated common rail injection mapping computer, with one of the most aggressive after-treatment strategies around. M-B says the key to the system is finally having the proper ultra-low-sulphur fuel in order to start the whole process as clean and strong as possible. After that, the first priority is making the burn in the engine as clean as possible. Next, a four-stage emissions cleaning system begins with the oxidization catalyst scrubbing out carbon monoxide and unburnt hydrocarbons. After that, the particulate filter collects 99 percent of the soot, and then burns it off when necessary during a computer-controlled regeneration process (much like a self-cleaning oven). Finally, an inert liquid (M-B calls it AdBlue but it's essentially a urea solution) into the exhaust, converting the remaining NOx molecules into harmless nitrogen and water vapor in the final selective catalyst reduction process. The result is the cleanest exhaust fumes you'll ever see or smell.
This system allows M-B to be the first diesel manufacturer (if you don't count Cummins' work-duty B-motors of last year -- offered only in Heavy Duty Rams) to be 50-state compliant before the 2010 deadline. In fact, M-B says it will also allow the maker to meet the next-gen European EU6 requirements coming in 2015.
We recently drove the ML 320 (and R320 and GL 320) BlueTEC over several one-hour and two-hour loops through the Vermont countryside around Manchester Center and into the Green Mountains, averaging 28.4 mpg. With 398 lb-ft of torque at 1400 rpm (210 hp at 3800 rpm), the engine is comfortable staying at 1800 rpm; no matter the hilly conditions, the engine has pulling power. It's worth noting there weren't many opportunities to get above 60 mph. Also of note, M-B has a wonderful seven-speed trans (complete with paddle shifters) ready to smoothly respond to any driver situation. Downshifts are quick and smooth. Put your foot to the floor and there is little hesitation, as the torque is strong enough to pull the SUV like a performance coupe through the powerband. The only giveaway in the cockpit is that the tach has a 4400-rpm redline, instead of the 6500-rpm point of the typical gas engine. Outside, the only giveaway are small BlueTEC badges on the tailgate and front fenders.