The Mercedes S-Class does everything a true, full-size luxury sedan should, and we might describe it as a complete automobile. If you need something, the S-Class almost certainly has it. If you want it to do something, just about anything, the S-Class can probably get it done.
Every S-Class delivers better than adequate power and performance in smooth, quiet, rock-steady fashion. Virtually all of its luxury or high-tech features are offered on all models, so how much better than adequate the performance gets depends on the buyer's budget or penchant for satisfyingly wretched excess.
There are substantial mechanical changes to the S-Class line-up for 2012, starting with three new engines intended to improve fuel economy without sacrificing power or performance. The standard seven-speed automatic has also been re-designed, basically for the same purpose. This transmission is engineered to help ensure that more of the engine's power gets delivered to the wheels to move the car, rather than bled off in the transition (and wasted) as friction and heat.
The highlight for 2012 is introduction of the S350 BlueTEC, the first diesel-powered S-Class available in North America in 16 years. It's driven by an advanced, 240-horspower, 3.0-liter turbo-diesel V6 engine through the seven-speed automatic, with standard 4MATIC all-wheel drive.
Mercedes' V6 turbodiesel is the smoothest, quietest diesel engine available, so virtually all the smoky, clattering drawbacks of more traditional diesel power are gone (though the oily diesel smell during fill-ups remains). The S350's 240 horsepower is impressive by diesel standards, and if it seems a bit light (or the engine a bit small) for a car the size of a Hummer H2, don't sweat it. This engine produces 455 pound-feet of torque, and it's the twisting power of torque that generates acceleration. Dip the accelerator pedal on the S350 BlueTEC and it jumps, with enough force to snap the head back into the headrest.
The S350's overall performance is virtually identical to the gasoline-powered S400 Hybrid, with even stronger short bursts of acceleration, and the diesel engine comes with a substantial fuel mileage increase compared to the hybrid, or any other car in this class (projected at 20 mpg city, 31 highway, according to the EPA). And that's with standard all-wheel drive, which works against fuel economy. Not that long ago, a 31 mpg highway rating was the domain of much smaller, slower cars. If our usual travel circle left access to diesel fuel, we wouldn't have a second thought about choosing the S350.
The S400 Hybrid does not meet some definitions of hybrid because it won't propel itself on electric power alone. Essentially, it uses its electric motor to add power without using more fuel, and it does improve mileage compared to the V8 models (19 mpg city, 25 highway, though we recorded 21.7 around town and 27.6 on the highway). Its compact lithium-ion battery is in the engine compartment, and the S400 weighs only 19 pounds more than S550. With a combined power output of 295 hp and broad torque delivery, its acceleration betters most hybrids, and it hits 60 mph from a stop in just over seven seconds. A hybrid- status dash display let's the S400 driver know what the electric motor is doing and how the battery is charged.
Several characteristics distinguish the S400 from the S550. The S400 Hybrid makes a different noise, not rougher or louder, merely different. It switches off automatically when coasting or stopped to save fuel, so the tachometer swings to zero. Taking your foot off the brake or touching the gas pedal restarts the engine, and it makes this transition more smoothly than any hybrid we can think of, including pricier V8s.
Overall, however, the S400 is a bit less smooth than the S550. In places where you're going very slowly, as you might creeping into a tight parking spot, the stop-engine feature may be more active than you'd like, but resting your big toe on the gas pedal to keep the gas engine running will smooth things nicely. The S400's brake pedal also feels more like an on/off switch, because it is, switching the electric motor to a generator that helps slow the car and charge the battery in the process. While the pedal may not be as smooth, the brakes still stop the S400 in short, drama-free, order.
The V8-powered S550 gets a new engine for 2012. It's 4.7-liter, twin-turbocharged V8 is smaller than the engine it replaces, with highly efficient direct fuel injection. The new engine increase fuel economy 20 percent (projected at 15 mpg city, 23 mpg highway), but it also produces 30 percent more power, with 429 horsepower and 516 pound-feet of torque. The S550 behaves a lot like the S400, except that it delivers substantially more thrust.
S-Class cars start in second gear to save fuel (unless you've chosen Sport or Manual modes), but even when starting in second gear, the S550 really scoots. Its turbochargers start spinning quickly, delivering viscerally charged, seat-of-the-pants acceleration almost out of character with the S-Class's size and stately demeanor. Mercedes reports 0-60 mph times of 5.4 seconds, and the optional 4MATIC gets the S550 going more easily in poor conditions.
Every S-Class is library quiet, and virtually free of wind noise at freeway speeds. Normal-volume conversations (with your driving instructor) can be maintained at 130 mph. Road noise increases nominally with the larger-diameter wheels, but the tire noise still won't be heard above a talk-radio program. Engine sounds are more pronounced in the AMG models, but these still cruise in subdued tones.
Ride quality is superb. The S-Class air suspension combines smoothness with complete control and utter stability as you waft along faster than you think. The suspension can be raised at slow speeds for speed bumps or driveway angles. It automatically lowers at higher speeds for stability and economy, and it can be firmed up in Sport mode if the driver prefers quicker reactions to pillow-gentle manners.
At any speed, the S-Class duly goes where it's pointed, as we discovered occasionally by accident. The sensation of speed can be muted in this car, but if you find yourself getting into an off-ramp a bit too fast, you'll be impressed by what this 4,500-pound mass can do, even before any electronics come into play to save you from your own poor driving habits. The steering is reasonably fluid, linear, predictable and surprisingly quick for such a long wheelbase. Until you are used to it, the car may turn more than you anticipated given the amount of movement on the steering wheel.
Some S-Class models speed the turns up by adding a touch of brake to a rear wheel to help rotate the car through the corner. Overall, the brakes are easily modulated and seemingly endless in their ability to shed speed faster the harder you depress the pedal.
Active Body Control (ABC) adds another element to suspension control by mechanically countering the forces of physics. It forcibly flattens the car's stance through a corner without making the suspension stiffer. It's like a motor race, where the driver swerves back and forth to warm or clean tires while the car appears to lean very little. ABC creates a similar effect in a much heavier, taller, softer riding road car, without wrecking ride quality.
The Distronic Plus adaptive cruise control option is another S-Class system that works well, even if it takes something like a leap of faith on the driver's part. It uses radar sensors to maintain a pre-set following distance behind the vehicle ahead, and it almost drives the car, working at up to 125 mph and braking to a full stop.
Set your speed on the freeway (and initially, the size of the gap you prefer to the car ahead), and the S-Class will maintain that speed until it closes on a car directly ahead, in which case it will slow itself to maintain the prescribed gap. If the car ahead speeds up, the S-Class will speed up. If the call ahead slows down, so will the S-Class, on its own, all the way to a complete stop. Or if you change lanes and clear the way ahead, the S-class will accelerate to the set speed. In the typical stop-and-go freeway commute, the S-Class can do all of the braking and accelerating for you. You just do the steering.
Distronic Plus also enables a feature called Parking Guidance. At low speeds, the system scans available parking spots and shows a "P" in the dash if the S-Class will fit in a parallel space. When you shift in reverse, the S-class won't back itself into the spot, as some other parking systems do. Rather, it displays a top-view pictogram of the car, showing everything around it, and provides steering guidance. We might like this approach better.
The S600, with its twin-turbo V12 engine, whirs and hums rather than starts and runs, with a fluidity matched only by more-expensive twelve-cylinder cars. It has a five-speed automatic, but with 510 hp and a prodigious 612 lb-ft of torque (at just 1800 rpm), the S600 does not suffer when it comes to acceleration. The S600 will run 0-60 in less than five seconds with four people on board, as long as you can find traction. The S600 comes standard with 18-inch wheels like lesser S-Class cars, but they are wider in back, with wider tires, to help harness the power.
The S63 AMG also gets a new engine for 2012: a larger version (5.5 liters) of the S550's twin-turbo V8. It, too, makes more power than the engine it replaces (536 hp, 590 lb-ft), but it's equipped with a start/stop feature like the S400 Hybrid, so it shuts itself off when the car is stopped or idling. The S63 also features a unique seven-speed automatic transmission that works like a conventional clutch-operated manual, without the clutch pedal. These changes improve fuel economy, and the S63 no longer carries a gas-guzzler tax.
The S63 is a different breed than the S600. It matches the S600 for speed but has crisper, racier response. With its extra-powerful V8 come extra-massive brakes, AMG-calibrated suspension, and 20-inch wheels with ultra-low profile tires. Every component is designed to maintain a torrid pace. The S63 is not the fastest S-Class but it is the most driver-oriented and the most sporting.
The S65 AMG is a wolf in sheep's clothing, marrying the leather-and-suede luxury of an S600 with the sporting chassis of an S63 and 6-liter twin-turbo V12. It generates 636 horsepower and a staggering 738 lb-ft of torque as smoothly as a jet engine, making your head the nail, the headrest a center-punch and your right foot the hammer. With more torque than just about anything on the road and twice the horsepower of a typical sport sedan, an S65 with traction control off can spin tires through 70 mph, or hit an electronically limited three-miles-per-minute top speed. It will accelerate ferociously from 60 mph to 120 faster than most cars will from a stop to 60, yet it's easily managed if you don't switch the anti-skid electronics off. We found it downright docile when driven moderately. Effortless is a wholly appropriate descriptor here, and maybe excessive. Yet this is the sort of car that makes economically challenged driving enthusiasts dream of winning the lottery, or envious of anyone who can actually afford one.