2014 Mercedes-Benz S550 review:

New S-Class takes the lead with self-driving tech

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At speed down the freeway, Steering Assist wasn't robust enough to keep the car in its lane without my help, and the car gave me a warning when I took my hands off the wheel. However, up to speeds of 18 mph, Mercedes-Benz says the system will keep you in your lane and won't bother you about keeping your hands on the wheel.

I was only in one, short traffic situation slow enough to test it, but, putting my faith in German engineering, I let go the wheel and was suitably impressed how the car drove itself.

2014 Mercedes-Benz S550
The instrument cluster changes to this screen when adaptive cruise control is active, showing when slower traffic is ahead. Josh Miller/CNET

One caveat, the system only works when the cameras can distinguish lane lines. A little steering-wheel icon turns green when the car meets that condition. I had to monitor that icon because, given often bad roadwork, it frequently wasn't able to get a lock on the lines.

Mercedes-Benz makes a raft of other driver assistance features available on the S550, including a night vision system. This model came with a blind-spot monitor, which flashed icons in the side mirrors when it wasn't safe to change lanes. Blind-spot monitors are one of my favorite safety features, and very helpful in the big S550. The backup camera also showed incredibly sharp detail, and the large LCD made possible a gigantic image, complete with trajectory lines to aid parking.

Eco or Sport
When I turned off cruise control and asserted full control of the S550, I found it an easy cruiser but tense when pushed. With 455 horsepower and 516 pound-feet of torque, the engine gives this big sedan more than enough push. Like Mercedes-Benz' other 550-designated models, the S550 gets a 4.6-liter V-8, which uses direct injection and twin turbos for efficiency and boost.

At the time of this review, Mercedes-Benz had not released the car's curb weight, but it puts the zero-to-60 mph time at 4.8 seconds, very respectable for this big roller.

2014 Mercedes-Benz S550
The S-E button toggles the car from Sport to Eco, and the Sport-Comfort button changes the air suspension setting. Wayne Cunningham/CNET

I appreciated how Mercedes-Benz kept the drive modes simple. The S550 is either in Eco or Sport, because why would you need any more granularity? An extra button adjusts the air suspension between Comfort and Sport, the former making it feel as if the car floats over potholes and bumps.

Around town and on the freeway, I left it in Eco mode, which softened the accelerator response, making it easier to creep in traffic and make sedate starts off the line that wouldn't jostle my passengers' cappuccinos. In this mode, stamping the gas pedal made it feel as if the car had to gather its power up before it would unleash it all with locomotivelike power.

The seven-speed automatic transmission shifted seamlessly through the gears, seeking the highest available for the speed. Whenever I glanced at the virtual tachometer, it sat at 1,500rpm, whether I was cruising city streets at 20 mph or barreling down the freeway at 70.

The electrically boosted power steering offered little resistance, making for easy maneuvering but numb response. Despite the huge cabin area, the S550 felt like a smaller car as I cut through traffic, taking advantage of openings for quick lane changes.

2014 Mercedes-Benz S550
The S550's turbocharged 4.6-liter V-8 produces plenty of power for the big sedan, and runs quietly. Josh Miller/CNET

Impressively, the S550's idle-stop feature wasn't annoying. Idle-stop shuts the engine down when you stop at a red light, and rival manufacturer BMW has had a difficult time making that feature work smoothly in its larger engine cars. In the S550, the engine generally runs so quietly that I had to check the tachometer to see when it was actually stopped. As I lifted off the brake pedal, the engine restarted with the gentleness of a small-displacement four-cylinder. I was able to turn off idle-stop at the touch of a button, but I found no need, and appreciated that the big V-8 wasn't burning gas as I sat for minutes at red lights.

As for fuel economy, Mercedes-Benz didn't have its official EPA numbers by the time of this review. The trip computer showed mid-20s on the freeway and high-teens in the city, about what I would expect. My average, including freeway, city, and some raucous back-road driving, came in at 18.2 mpg.

With the S550's engine and suspension in Sport modes, it transforms into that Anonymous Baddie Car for chasing down James Bond. And showing a good sense of place, it wouldn't likely run him down. Nimble is not a word I would use for the S550, and it wouldn't be my first choice for racing through the bends on a good road.

It handled high speed decently, but the air suspension, even in Sport mode, couldn't keep it flat in the turns. Mercedes-Benz offers an option called Magic Body Control, not equipped on the car I tested, which not only exerts more active suspension response in the turns, but uses the car's cameras to analyze the road surface and respond with an appropriate ride program. That option might make the car handle tight turns better and contribute to an even more comfortable ride.

2014 Mercedes-Benz S550
Heavily boosted electric power steering makes the wheel very easy to turn. Josh Miller/CNET

Putting the engine in Sport mode made the gas pedal almost too responsive. My smallest input led to surges of power, unexpected considering the much more docile Eco performance. Personally, I would like the Sport response toned down just a bit, but your average James Bond-chasing villain may prefer the more sensitive pedal.

The transmission also takes on a different character in Sport mode, letting the tachometer needle run rampant around its dial. I was impressed when, braking heavily before a corner, the transmission geared down quickly, then held the engine at a solid 4,500rpm as I made the turn exit.

The S550 came equipped with paddle shifters on the steering wheel, and the transmission allowed quick manual shifts. However, I could not find a means of keeping the car in manual mode. Whenever I left the paddles untouched for a couple of minutes, such as on a straight, the transmission switched back to automatic shifting.

A bold step forward
With the 2014 S550, Mercedes-Benz shows what a flagship sedan should be. This car debuts new technologies and plants the Mercedes-Benz marque firmly in the future. Impressively, Mercedes-Benz doesn't coddle older buyers who might feel uncomfortable with virtual gauges, LED lighting, and near-autonomous features, instead implementing available advances that improve driving comfort and safety.

Steering Assist may seem radical, but it represents the same type of step forward Mercedes-Benz made previously with its Distronic Plus adaptive cruise control.

The tech features in the new S550 are almost too numerous to mention, and most are implemented successfully. The massive center LCD makes cabin tech features less distracting, as well-designed screens make it easy to pick up information at a glance. The LCD instrument cluster could use a better 3D look, but it represents the wave of the future for cars.

Fuel economy may be middling, but the S550's engine shows off a good set of modern efficiency and power technologies, and its seven-speed automatic transmission responded well in both Eco and Sport modes. Mercedes-Benz also implemented an idle-stop feature worthy of the company's luxury brand.

Navigation and audio systems are also top-notch, and the Burmester audio system is a delight to the ears. App integration remains the one weak spot in this technology cornucopia. Mercedes-Benz gave the S550 more apps than on its previous models, but the company needs to negotiate a better, always-on data connection for the car.

Tech specs
Model 2014 Mercedes-Benz S550
Trim Base
Power train Turbocharged direct-injection 4.6-liter V-8, 7-speed automatic transmission
EPA fuel economy Not available
Observed fuel economy 18.2 mpg
Navigation Standard hard-drive-based system with traffic
Bluetooth phone support Standard with contact list integration
Digital audio sources Internet-based radio, onboard hard drive, Bluetooth streaming, iOS integration, USB drive, SD card, HD Radio, satellite radio
Audio system Burmester system
Driver aids Optional adaptive cruise control with steering assistance, blind-spot monitor, backup camera, night vision, surround-view camera, lane-keeping assistance, massage seats
Base price Not available at time of review
Price as tested Not available at time of review

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