2015 Mercedes-Benz C-class review: This sedan raises the bar for midsize luxury

Pricing Unavailable
  • Available Engine Gas
  • Body style sedan

Roadshow Editors' Rating

7.0 Overall
  • Performance 7
  • Features 8
  • Design 6
  • Media 7

The Good The 2015 Mercedes-Benz C400 comes with standard LED headlights, a sweet-sounding Burmester audio system and road-gripping all-wheel drive. Optional driver assistance features verge on self-driving technology.

The Bad Connected infotainment features are crippled by an always-off Internet connection and the head-up display graphic is too large.

The Bottom Line The 2015 Mercedes-Benz C400 makes for a very comfortable and occasionally sporty drive, and advances the idea of a midsize luxury sedan, setting a new bar for the competition.

When Mercedes-Benz released its new S-class in 2013, it set a higher standard for technology in luxury cars. With the redesign of the C-class for the 2015 model year, the company shows that, rather than a trickle, technology floods down the lineup.

The 2015 Mercedes-Benz C400 impressed me with its smooth lines and LED headlights when it first showed up in the CNET garage. Soon I was to discover that not only are the LED headlights standard, so is a Burmester audio system. As for optional features, this C400 came with the full range of driver assistance systems I saw in the S-class, and which sets Mercedes-Benz on the path toward autonomous vehicles.

The C-class, Mercedes-Benz's luxury midsize sedan, comes as the C300 and C400 in the US, with turbocharged four-cylinder and six-cylinder engines, respectively. All-wheel-drive is available on the C300 and standard with the C400. Base price for the C400 comes in at $48,590, although my heavily optioned example hit $63,705. UK C-class buyers enjoy a choice of multiple gasoline and diesel engines, but nothing above four cylinders, with a base price of £26,855. Likewise, Mercedes-Benz keeps the C-class down to four cylinders in Australia and offers a base model for AU$66,626.

Efficient downsizing

The C400 follows a general trend of downsizing engines to gain fuel economy, in this case using a 3-liter V-6. Direct injection and twin turbochargers, one for each bank of cylinders, drive output to 329 horsepower and 354 pound-feet of torque. The C300 employs a turbocharged 2-liter four-cylinder, making 241 horsepower and 273 pound-feet of torque.

In another new twist for Mercedes-Benz, the C400 included five different drive modes: Eco, Comfort, Sport, Sport Plus and Individual. Each mode regulated settings including throttle sensitivity, steering response and suspension. I was able to select each mode using a toggle switch labeled "Agility," and I could save custom settings in the Individual mode.

2015 Mercedes-Benz C400
Mercedes-Benz adds an Agility switch to the C-class, taking it from Eco to Sport Plus modes. Wayne Cunningham/CNET

The impressive power figures from the C400's engine were somewhat diminished by the seven-speed automatic transmission. In Eco or the default Comfort modes, the transmission was slow to downshift when I floored the gas pedal to pass other cars. Likewise, while barreling down a twisty road in Sport and Sport Plus, using the steering wheel-mounted paddle shifters, laggy gear changes kept me from really exploiting the power.

And generally on the road, I found the transmission's gear changes much more noticeable than they should be in a luxury car, suggesting a need for refining the shift programming.

Included on this car was the optional Airmatic suspension, a surprising addition for a midsize vehicle from any manufacturer. However, I didn't feel the C400 glide over the road as smoothly as the S-class. That's not to say it wasn't a very comfortable ride, just not quite as nice as in cars further up the line. The suspension proved itself very competent in Sport and Sport Plus modes, the more sensitive steering program giving me good response from the wheel on twisty roads at speed.

Even better, the C400's standard all-wheel-drive system proved itself on the wet roads I was driving. Taking it out on a rainy day, I could feel the torque shift when I kept the speed up in the turns. The rear wheels felt ready to let go, but the fronts clawed forward, working with the car's traction and stability systems to hold the road.

2015 Mercedes-Benz C400
Standard all-wheel drive on the C400 leads to good road-holding in the wet. Wayne Cunningham/CNET

Helping the C400 earn its EPA fuel economy rating of 21 mpg city and 29 mpg highway, an idle stop system shut the engine down when I stopped at traffic lights. I didn't find this system too intrusive, quickly starting up the engine when I left off the brake in plenty of time to let me roll forward with traffic. Those fuel economy numbers are good for a modern engine of this size, and should allow mid-20s average fuel economy. I pulled an average of 22.6 mpg for driving that included all modes, from Eco to Sport Plus.

Hands-off driving

Mercedes-Benz excels in driver assistance systems, and the C400 benefits from the full array. Setting my preferred speed for the adaptive cruise-control system, lane-keeping automatically engaged, using forward-looking cameras to monitor the lane lines and help steer the car. Having previously experienced this system on the S-class and E-class, I found that it works every bit as well on the C-class. Testing the C400 on the freeway, it lit up a warning screen when I took my hands off the wheel and let it steer. However, at speeds under 20 mph, such as very slow traffic, I could let the car handle the steering, as long as the green wheel icon was lit, showing the car could actually see the lane lines.

2015 Mercedes-Benz C400
The C-class' new Agility modes change steering, throttle and suspension settings. Wayne Cunningham/CNET

This C400 included a new feature, which I hadn't previously seen from Mercedes-Benz, a head-up display projecting onto the windshield. I liked the clear imagery from this optional system, but Mercedes-Benz doesn't make much use of it, only showing speed and turn-by-turn directions. I would have also liked information about the adaptive cruise control setting, showing me actual speed versus set speed. This head-up display was also a bit too intrusive, using a large image occupying too much of my view.

The C400 also exhibited some upgrades to Mercedes-Benz's venerable Comand infotainment system, but it still falls behind those of BMW and Audi. The system consists of a high-resolution 8.4-inch LCD and a dial on the console. In addition, Mercedes-Benz includes a row of buttons on the center stack giving quick access to navigation, stereo and phone controls, a useful update. There is also a touchpad extending over the console dial. However, this touchpad only let me swipe through some menus -- it did not offer character tracing, forcing me to use the dial to manually enter alphanumeric characters.

Voice command remains a very good option for entering destinations, making phone calls and requesting music from onboard sources. The system offers comprehensive commands and works well.

Where previously the Comand interface showed drop-down menus from a list of major function areas along its top bar, in the C400 it brought up a whole submenu, letting me use the dial to scroll through audio sources, vehicle settings or navigation options. This new scheme looks nicer, but ends up requiring more steps to complete an action. I think it's time Mercedes-Benz rethought this entire interface.

2015 Mercedes-Benz C400
Adaptive cruise control and the lane departure prevention system let you take your hands off the wheel in slow traffic. Wayne Cunningham/CNET

Always-off Internet

I found quite a few new connected features in the C400, such as Google maps for the navigation system, Internet-based radio stations, Google search and various apps built into the car. These features would have been nice if the C400 did not suffer from the same achingly slow Internet connection as I have seen in other Mercedes-Benz models. I spent far too much time looking at the Establishing Internet Connection screen before I could actually access any of the car's connected features.

As in other Mercedes-Benz models, the C400 gets a reasonably fast 3G data connection, but instead of being always on, the car needed to reestablish its connection every time I tried to access an app. This seems to be a problem with Mercedes-Benz's US data supplier, so it's likely not a problem in other markets, and certainly not a problem I've seen with BMW or Audi connected services. The C400's data connection, frankly, makes its connected features unusable.

2015 Mercedes-Benz C400
Mercedes-Benz includes many apps in the C400, but the data connection is too slow for them to be usable. Wayne Cunningham/CNET

As for onboard features, I was pleased with the look of the navigation system's maps and the quality of route guidance. The maps showed 3D rendered buildings and offered good traffic coverage. Online destination search shows up in a menu alongside points-of-interest and manual address entry, but I wouldn't recommend using it due to the lengthy connection times.

Audio sources include HD Radio, Bluetooth streaming, satellite radio, two USB ports for iOS devices and drives and an onboard hard drive. I particularly like the music library interface for drives and my iPhone, which let me search by keyword or scroll through album covers along with the usual artist, album or track listings.

The Burmester audio system, using 13 speakers and a 590-watt amp, was a particular standout, and very nice as a standard feature. Mercedes-Benz builds what it calls Frontbass into the structure of the C400, using space within the body of the car as a resonance chamber for the woofers, allowing the kind of bass response you get with cabinet speakers. I found the audio quality to be very clean, with crystal-clear vocals and instrumentation. The Frontbass lived up to its promise as well, giving me very palpable low frequencies. The bass came though in a controlled manner without overwhelming the listening experience.

2015 Mercedes-Benz C400
You can view song titles, turn-by-turn directions and driving information on the C400's instrument cluster display. Wayne Cunningham/CNET

S-class wannabe

The 2015 Mercedes-Benz C400 may fall short of being a baby S-class, lacking that car's gliding ride quality, but I found it very enjoyable, a comfortable place to be when slogging through city, cruising the freeway or driving hard on backroads. The new C-class captures Mercedes-Benz's luxury character and uses technology to set a good standard for midsize sedans. This new engine offers good power and economy, although I felt the transmission programming needs more refinement.

The different driving modes give flexibility to the C400, and I like how they affect all driving settings at the flip of a toggle switch. However, Sport Plus overpromises for the C400's capabilities. If you want a real hard-driving C-class, look to the new C63 AMG based on this new generation.

The infotainment system looks good and shows off some positive new developments, but it seriously suffers from the data connection. The lack of quick access to online destination search and the multitude of apps in the car puts Mercedes-Benz at a disadvantage against BMW and Audi. Likewise, the touchpad does not offer the same flexibility as those in Audi and BMW vehicles.

Where the C400 shines is the availability of advanced driver assistance systems. Mercedes-Benz is at the forefront of developing features such as adaptive cruise control and lane keeping, the latter of which almost amounts to self-steering. These are important technologies on the road to self-driving cars. More useful for the everyday driver, they take stress off during long drives and promote safety.

Tech specs

Model 2015 Mercedes-Benz C-class
Trim C400
Powertrain Turbocharged 3-liter V-6 engine, seven-speed automatic transmission
EPA fuel economy 21 mpg city/29 mpg highway
Observed fuel economy 22.6 mpg
Navigation Optional with live traffic
Bluetooth phone support Standard
Digital audio sources Internet streaming, Bluetooth streaming, onboard hard drive, iOS integration, USB drive, HD Radio, satellite radio
Audio system Burmester 590-watt 13 speaker system
Driver aids Head-up display, lane departure prevention, adaptive cruise control, blind spot monitor, rear view camera
Base price $48,590
Price as tested $63,705