By Steven Cole Smith
The Orlando Sentinel
If you haven’t driven one in a decade or so, forget what you thought you knew about Rudolf Diesel’s 1883 invention — that diesel engines are noisy, smoky, heavy, substantially more expensive to build, and slow. Though light-duty diesels haven’t caught on in the U.S., there’s a reason why they dominate plenty of European markets where fuel costs about double what we pay.
In smaller cars, gasoline engine technology has risen to the point where the diesel engine has lost some of its fuel-mileage edge. The 2012 Volkswagen Golf diesel has an Environmental Protection Agency average of 34 mpg, while the gasoline-powered 2012 Hyundai Elantra averages 33 mpg. With diesel averaging about 27 cents a gallon more than regular gas in the U.S., the diesel engine will actually cost more in fuel.
But in larger vehicles — full-size trucks and SUVs, for example — diesels rule. Example: The new 2012 Mercedes-Benz ML350 BlueTEC, a heavy-duty, five-passenger SUV with a 3-liter, 240-horsepower turbocharged diesel V-6 engine. Mercedes expects the EPA to rate it at 20 mpg in the city and 25 mpg on the highway. In 400 miles of driving, we averaged just over 24 mpg — excellent for a full-time all-wheel-drive sport-ute that can tow 7,200 pounds.
The 2012 M-Class is the third generation for the vehicle, which was the first vehicle built in Mercedes-Benz’s Alabama plant. The regular ML350 is powered by a 3.5-liter, 302-horsepower V-6. While the gasoline engine has the horsepower edge over the diesel, the diesel has 455 pound-feet of torque, compared to 273 pound-feet for the gas engine. This is one reason why diesels work so well in larger vehicles — torque is a better measure of pulling power than horsepower.
Pulling power and a low-RPM operating range has in the past meant pretty leisurely acceleration for diesels, but the Mercedes overcomes that by turbocharging the engine, and mating it to an intuitive seven-speed automatic transmission that maximizes the engine’s capability. Mercedes claims a 0-to-60 mph time of 7.3 seconds, exactly the same as for the gasoline-powered model, which is EPA-rated at 19 mpg overall. The diesel version does tip the scales at more than 5,000 pounds — about 275 pounds more than the gas-powered model — but neither version is a lightweight.
Really, that’s the only negative to the diesel, except for a modest price premium of about $1,500 — it’s quiet, smoke-free and essentially indistinguishable from a gas engine.
So how does the rest of the M-Class work? Quite well, but it feels a lot different than the ML320 that kicked off Mercedes’ mainstream SUV efforts in 1998. The word “overbuilt” comes to mind, and that’s a compliment: The ML350 seems more muscular and solid than the previous two generations. Interior appointments are as nicely done as any Mercedes sedan, with lots of standard features, such as a power tailgate, sunroof, DVD video and audio player and eucalyptus wood trim. Front- and rear-seat room is excellent, and since there was no third-row seat, cargo space is generous, up seven cubic feet from last year.
The test vehicle had a lot of options, many of which I could do without, which raised the $50,490 base price to $64,335. On pavement, handling is better than you’d expect for a heavy vehicle, and while the M-Class really isn’t designed to go off-road, it’s surprisingly nimble on some pretty challenging trails, aided by a set of Continental radial tires that work equally well on and off the road.
As modern as the 2012 ML350 BlueTEC is, there’s an old-school sense of capability that owners will find assuring. Mercedes in general, and the employees of the Tuscaloosa County plant in particular, have learned a lot about building SUVs since 1998.
Steven Cole Smith is the automotive editor for the Orlando Sentinel.
