2014 Mercedes-Benz E550 Cabriolet review:

E550's tech eases driving, but apps are useless

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2014 Mercedes-Benz E550 Cabriolet
HD radio offers clearer audio production and shows more song data than conventional FM. Josh Miller/CNET

Bluetooth audio streaming was the easiest option for any smartphone user. However, the E550 Cabriolet did not have the Bluetooth Host Controller Interface stack, so I had to use my phone to select music.

For other onboard audio sources, I could select music using voice command or through the music library interface on the LCD. Along with the usual lists of artists and albums, I really liked the album cover display, which was a less distracting means of choosing music.

The music I chose, whether played from a CD, over Bluetooth, or from a USB drive, was greatly enhanced by the car's Harman Kardon audio system. With 14 speakers, including a center channel and subwoofer, this system produced music with fine detail. The output was very balanced between bass and treble, offering extended frequency response. A 610-watt amp brought out subtle sounds and instruments from the tracks I fed through this system. The metal grilles on the speakers were also a nice touch.

Gentle power
Under the hood was another sort of amp, this one using two banks of four pumping pistons displacing 4.7 liters. Gasoline was shot into the cylinders through direct injection and twin turbochargers forced air into the mix. The standard V-8 for current 550-designated Mercedes-Benz models, this engine produces 402 horsepower and 443 pound-feet of torque, a walloping amount of power for this 4,000 pound car.

2014 Mercedes-Benz E550 Cabriolet
This turbocharged V-8 has become the standard mill for Mercedes-Benz's bigger cars. Josh Miller/CNET

As is standard with most Mercedes-Benz models these days, that engine was mated to a seven-speed automatic transmission. Lacking a conventional shifter, I had to use a stalk on the steering column to select drive modes. Showing the E-Class' age a bit, the car had a pedal to engage the parking brake rather than an electronic control.

Despite the large engine and power output, the E550 Cabriolet proved surprisingly economical. Its 17 mpg city estimate isn't great, but on the freeway, the trip computer registered an average above the 26 mpg highway rating. Driving in the city took a toll on the fuel economy, but not as much as I would have expected. The E550 Cabriolet's Eco button's sole purpose is to engage the engine's idle-stop feature, shutting down the big V-8 at every stop light.

I wouldn't expect idle-stop to work well with a V-8, but Mercedes-Benz has its system perfected. The engine started quickly and unobtrusively whenever I took my foot off the brake. The same could definitely not be said for the CLA250 I reviewed earlier, even though it had a much smaller engine.

The air suspension and the easily turned steering wheel made the E550 Cabriolet a comfortable and virtually effortless car to drive. The suspension in particular soaked up any rough patches in the road. Although I only took the car on day trips, I imagine it would be very nice for an extended road trip, if you could find someplace to put your luggage.

2014 Mercedes-Benz E550 Cabriolet
An air suspension makes for a very smooth ride. Josh Miller/CNET

The size of the engine might seem a bit much for a medium-sized four-seat convertible, but it was certainly nice to have that power on tap. At idle, the engine burbled quietly with a deep note, giving a hint at what it could do. Under even moderate acceleration, it let loose an enjoyable growl.

Mercedes-Benz has its AMG brand for serious performance cars, leaving the E550 Cabriolet to be a dilettante when it comes to hard driving. Both the transmission and the suspension had sport modes. The buttons for both were plastic and it seemed as if Mercedes-Benz engineers mounted them on the console without much regard for taste or style.

Sport mode for the suspension was palpably different from Comfort. I felt the bumps in the road more and the ride became more rigid, but it didn't degrade to harsh. It dealt with bumps like a well-tuned fixed suspension, damping out any secondary jouncing. In the turns the E550 Cabriolet handled well, its rear-wheel-drive dynamics apparent, but the suspension remained a bit rubbery. The steering boost was unaffected, with the wheel maintaining its light, over-boosted feel.

Putting the transmission into its sport mode made it hold low gears depending on how aggressively I drove -- powering up to a turn and jamming on the brakes made it shift down. It held the low gears for extended periods, even as the tach needle spun up to 6,000.

Mercedes-Benz didn't choose to give the accelerator a sport mode, something I've seen on cars ranging from Mazdas to BMWs. Instead, driving at high revs made the accelerator much more sensitive, with millimeters of travel causing a substantial reaction from the engine.

Ultimately, I wasn't sold on the idea of sport modes for the E550 Cabriolet. I think it would make more sense if Mercedes-Benz had a single button that would not only set the transmission and suspension in sport, but also change the steering and accelerator tuning.

Sometimes autonomous
From both a traditional and a modern standpoint, the 2014 Mercedes-Benz E550 Cabriolet embodies luxury. The engine gives the car an easy power, always ready to do your bidding, while the air suspension delivers about the best automotive ride quality attainable. Surprisingly, fuel economy is not bad either.

Another area where Mercedes-Benz excels is in its driver assistance features. The company pioneered adaptive cruise control, and has now refined it to the point where it works in stop-and-go traffic. Add in Steering Assist, and the car is occasionally autonomous. The car can take over the burden of driving in severe traffic, exactly the sort of situation where you would want a chauffeur.

The audio system makes for another arrow in the luxury quiver, but not all is rosy among the cabin electronics. The navigation system shows maps with a quality to match the car, and the route guidance works very well. The interface to access all these features is dated, however, and could use some refinement. Mercedes-Benz revealed some of its future direction in the new S550, which includes a touchpad for electronics control, but the basic interface remains the same. Likewise, app integration is still an afterthought, and needs a more robust data connection to be really usable.

Tech specs
Model 2014 Mercedes-Benz E550 Cabriolet
Powertrain Turbocharged direct-injection 4.7-liter V-8 engine, seven-speed automatic transmission
EPA fuel economy 17 mpg city/26 mpg highway
Observed fuel economy 23.1 mpg
Navigation Optional, with live traffic
Bluetooth phone support Standard
Digital audio sources Internet streaming, Bluetooth streaming, onboard hard drive, iOS integration, USB drive, satellite radio, HD radio
Audio system Harman Kardon 14-speaker 610-watt system
Driver aids Adaptive cruise control, steering assist, automated parking, lane-departure warning, blind-spot monitor, surround view cameras, rearview camera
Base price $67,300
Price as tested $76,235

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