2012 Mercedes-Benz ML350 Road Test

Gas or Diesel? There's No Bad Choice To Make

Published: 07/19/2011  - by Erin Riches, Deputy Editor

Driving in Montana changes you, and after just a day here, we have no desire to be in anything smaller, lighter or less comfortable than the 2012 Mercedes-Benz ML350.

Everything about this state is huge, whether you're talking about mountains, glaciers or total square mileage. You'll never really get anywhere unless you're moving quickly, even if that means pounding down an old, twisty two-lane road at 70 mph (the posted limit even on obscure routes like state highway 279).

Midsize luxury crossover SUVs like the Mercedes-Benz M-Class have always been good at carrying your stuff, but nobody expects to make time on back roads. Thanks to more powerful V6 engines and an improved automatic transmission, the 2012 Mercedes-Benz ML350 and the diesel ML350 Bluetec hustle quite nicely. It's their improved mileage figures that make them good companions out there, though, as we haven't passed a fuel station for the last 50 miles.

It's Redesigned. Can You Tell?
It still looks like a used bar of designer soap to us, but the M-Class form is now a classic (at Montessori schools everywhere), so Benz is sticking with it for the third generation. Crisp, new sheet metal is stretched over the same 114.8-inch wheelbase as last year's model, although the redesigned SUV's track is over an inch wider. The 2012 ML350 is nearly an inch longer overall (189.1) while its height has come down nearly an inch (70.7).

Really, this midsize crossover didn't need to grow any larger. Although published legroom and cargo capacity have dipped slightly from the second generation, there's still ample knee clearance for 6-footers in the second row and, for the first time ever, you can recline the rear seatbacks. The 36.2-cubic-foot cargo bay is deep for this class, with space enough for two weeks' worth of groceries for a family of four.

It's also deep enough to package a third-row seat, and Mercedes is working on a fold-flat unit, even though the 2006-'11 M-Class didn't have one.

"It's about two years out," Steve Cannon, vice president of marketing for Mercedes-Benz USA, tells us. The take rate on this optional two-seat bench will be low, he adds, but it will target a vocal minority of owners whose beautiful, talented children are on club soccer teams.

Gasoline V6 Gets Direct Injection
You'll likely be more interested in the upgraded V6 engines on the 2012 M-Class.

Our 2012 Mercedes-Benz ML350 tester gets the same direct-injected, gasoline 3.5-liter V6 we've sampled in the 2012 C-Class Coupe and sedan. Power ratings don't change on the M-Class, so we're still talking about 302 horsepower at 6,500 rpm and 273 pound-feet of torque from 3,500-5,250 rpm. This is on par with the Acura MDX, but still shy of the 300 lb-ft of torque on the BMW X5.

Although smooth, the direct-injected V6 doesn't feel anywhere as potent in the nearly 5,000-pound ML as it does in the C-Class. Its best power comes at higher rpm, and when we step out to pass on Highway 200, we wish for more low-end grunt. Of course, there's a difference in elevation between Montana and Spain (where we drove the 2012 C350), so we'll wait until we test the 2012 Mercedes-Benz ML350 in Southern California before we get any more opinionated. Mercedes predicts a 7.3-second 0-60-mph time, which is over a half-second quicker than the old ML350.

An upgraded seven-speed automatic transmission makes the best of the situation, too, serving up quick downshifts when we need them. It drives all four of the 2012 ML350's wheels through the carryover 4Matic clutch-type all-wheel-drive system (a rear-drive ML350 is coming for the 2013 model year). Gear ratios are the same as last year's, but various friction reduction measures, plus a new torque converter that locks up in every gear, increase efficiency. The final drive is tamer at 3.67 versus 3.90 previously.

With all the improvements, the 2012 Mercedes-Benz ML350 earns a respectable 17 city/22 highway mpg EPA rating — a huge leap over the 2011 model's 15/20 rating.

But You Should Get the Diesel
Only 20 percent of Mercedes M-Class buyers bring home the diesel model, and you should count yourself in that minority if you're serious about getting an ML.

With a base price of $51,356, a diesel-powered 2012 ML350 Bluetec, equipped with the same seven-speed automatic and 4Matic system, costs just $1,500 more than our gasoline ML350. It gets to 60 mph in the same 7.3 seconds, says Mercedes, but is expected to earn a 20 city/25 highway mpg rating (versus 18/25 in 2011).

On the road, the diesel has none of the gas V6's high-rpm bravado, but you don't have to wait around for torque. The revised turbocharged and direct-injected 3.0-liter V6 provides an incredible 455 lb-ft from 1,600-2,400 rpm, along with 240 hp at 3,600 rpm. This engine made just 210 hp and 400 lb-ft on the 2011 model; the diesel X5 is rated at 265 hp and 425 lb-ft.

Reductions in internal friction led the way to the power and efficiency gains on the 2012 Mercedes-Benz ML350 Bluetec. Benz engineers have, for example, ditched the 3.0-liter engine's cast-iron cylinder liners (saving 9.5 pounds) and adopted the same cylinder wall coating process used on AMG engines. Another major contributor is a revamped common-rail injection system, which can inject fuel at higher pressure up to five times during a cycle — allowing the engine to do more with lower fuel volumes.

The 2012 ML350 Bluetec also uses a new, smaller turbocharger. The point here wasn't to increase power, but to hasten response when you floor the throttle.

Where's My V8?
About 8 percent of M-Class buyers still insist on a V8, and those are coming in the first quarter of 2012. The 2012 ML550 will use the new twin-turbocharged direct-injected 4.7-liter V8 engine, and although Mercedes officials don't want to discuss it just yet, the ML63 AMG will almost certainly show up with the 5.5-liter V8, also with twin turbos and direct injection.

"There's still demand for V8s, but it won't last forever," Cannon says, nodding in the direction of tighter fuel economy standards coming mid-decade.

"Over time, we have a turbocharged, direct-injected six-cylinder that we see replacing the V8s, though V8s will remain in the CLS-Class and above."

Don't wait up for an M-Class hybrid, as Mercedes won't be using the technology on the 2011 ML450 Hybrid anymore. Instead, the automaker is working on a parallel hybrid system with a clutch pack as the mediator (à la Hyundai Sonata Hybrid). The E-Class is first in line for hybridization; the ML will get it eventually, but maybe not in this generation.

Subtle Chassis Changes
The basic suspension design hasn't changed on the 2012 Mercedes-Benz M-Class, as you still have double wishbones in front and a four-link arrangement in back, but some of the particulars have changed.

Ride quality is exceptionally compliant with the standard setup of steel springs and conventional dampers, but the body roll is a bit much on the twisty downhill grades on Highway 200. Should you get out of hand, the latest version of the optional Lane Keeping Assist will aggressively intervene with steering wheel vibration and brake application to nudge you back to your side of the double-yellow, so best to keep a clean line.

New for 2012 is the Dynamic Handling package, which includes air springs, driver-adjustable adaptive dampers and adaptive antiroll bars, along with 20-inch wheels (in lieu of the standard 19s). Select Sport mode and, sure enough, the ML350 takes a much flatter attitude through these corners. However, unless you live in Montana, we can't see dropping $5,150 for this package.

The other big change in the chassis department is a switch to full electric-assist power steering — there's no hydraulic pump anymore. Oftentimes, this is bad news, but EPS is well executed on the M-Class. This is actually a variable-ratio setup, thanks to variable spacing of the gear teeth on the steering rack, and the result is precise steering with a logical build-up in effort as you turn the wheel off center.

Brake hardware is the same as last year, as the ML350 has 13-inch ventilated front discs with two-piston sliding calipers and 12.8-inch solid rear discs with single-piston calipers.

Come November, you'll be able to get an off-road package on both the gasoline ML350 and the ML350 Bluetec. In U.S. specification, it won't include low-range gearing, but will have a multi-terrain system that tailors drivetrain and suspension behavior to selected conditions as on the Jeep Grand Cherokee.

Not Going to Downsize
Of course, there's no shortage of tech features to add to the 2012 Mercedes-Benz ML350 and ML350 Bluetec, including a hard-drive-based navigation system, all-speed adaptive cruise control, a self-parking system and even accessory iPad docking stations for the backseat. No surprise, then, that our ML350 lands well past $60,000.

Among midsize luxury crossover SUVs, the Acura MDX and Lexus RX 350 are far less expensive, and they're both more rational choices if you're a minivan avoider just looking for functionality.

But nobody looks at a Benz for solely rational reasons, and so the ML's chief rival remains the BMW X5. The BMW is quicker with either its gas or diesel six-cylinder, and there's little doubt we'd have more fun chucking it into a corner on Highway 200. However, much like the current E-Class, the 2012 Mercedes-Benz ML350 feels greater than the sum of its parts.

This is a refined and comfortable vehicle that's all suited up for family duty, yet every bit as elegant as you'd expect of a vehicle with a big bottom line. Mercedes hopes to sell 36,000 MLs in a full calendar year, and if we lived in Montana we would gladly drive one every day.

Edmunds attended a manufacturer-sponsored press event to facilitate this report.