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The C-Class Cabriolet’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The 718 Boxster doesn’t offer pre-crash pretensioners.
The C-Class Cabriolet offers all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The 718 Boxster doesn’t offer all-wheel drive.
The C-Class Cabriolet’s optional lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane and gently nudges the vehicle back towards its lane. The 718 Boxster doesn’t offer a lane departure warning system.
The C-Class Cabriolet offers an optional Surround View System to allow the driver to see objects all around the vehicle on a screen. The 718 Boxster only offers a rear monitor and front and rear parking sensors that beep. That doesn’t help with obstacles to the sides.
To help make backing safer, the C-Class Cabriolet’s optional cross-path warning system uses wide-angle radar in the rear bumper to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. The 718 Boxster doesn’t offer a cross-path warning system.
The C-Class Cabriolet’s driver alert monitor detects an inattentive driver then sounds a warning and suggests a break. According to the NHTSA, drivers who fall asleep cause about 100,000 crashes and 1500 deaths a year. The 718 Boxster doesn’t offer a driver alert monitor.
Both the C-Class Cabriolet and the 718 Boxster have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights and rearview cameras.
The Mercedes C-Class Cabriolet weighs 663 to 1068 pounds more than the Porsche 718 Boxster. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.
There are over 2 times as many Mercedes dealers as there are Porsche dealers, which makes it much easier should you ever need service under the C-Class Cabriolet’s warranty.
The 718 Boxster’s redline is at 7500 to 8000 RPM, which causes more engine wear, and a greater chance of a catastrophic engine failure. The C-Class Cabriolet has a 6500-RPM redline.
J.D. Power and Associates’ 2019 Initial Quality Study of new car owners surveyed provide the statistics that show that Mercedes vehicles are better in initial quality than Porsche vehicles. J.D. Power ranks Mercedes 12th in initial quality. With 2 more problems per 100 vehicles, Porsche is ranked 15th.
The C-Class Cabriolet has 3.2 gallons more fuel capacity than the 718 Boxster’s standard fuel tank (17.4 vs. 14.2 gallons), for longer range between fill-ups.
In its Green Vehicle Guide, the U.S. Environmental Protection Agency (EPA) rates the Mercedes C-Class Cabriolet higher (6 out of 10) than the Porsche 718 Boxster (3). This means the C-Class Cabriolet produces up to 23.4 pounds less smog-producing pollutants than the 718 Boxster every 15,000 miles.
The Mercedes C-Class Cabriolet comes standard with an automatic transmission, for driver comfort, especially in the city. Automatic costs extra on the 718 Boxster.
A nine-speed automatic is standard on the Mercedes C-Class Cabriolet, for better acceleration and lower engine speed on the highway. Only a seven-speed automatic is available for the 718 Boxster.
All wheel drive, available in the C-Class Cabriolet, provides the best traction for acceleration in wet, dry, and icy conditions. In corners, all wheel drive allows both outside wheels to provide power, balancing the car. This allows for better handling. The Porsche 718 Boxster is not available with all wheel drive.
The C-Class Cabriolet’s standard 245/40R18 rear tires provide better handling because they have a lower 40 series profile (height to width ratio) that provides a stiffer sidewall than the 718 Boxster’s standard 45 series tires.
Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires standard on the C-Class Cabriolet can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The 718 Boxster doesn’t offer run-flat tires.
The C-Class Cabriolet offers an optional space-saver spare tire so you can replace a flat tire and drive to have the flat repaired or replaced. A spare tire isn’t available on the 718 Boxster, it requires you to depend on roadside assistance and your vehicle will have to be towed.
The C-Class Cabriolet’s drift compensation steering can automatically compensate for road conditions which would cause the vehicle to drift from side to side, helping the driver to keep the vehicle straight more easily. The 718 Boxster doesn’t offer drift compensation steering.
For a smoother ride and more stable handling, the C-Class Cabriolet’s wheelbase is 14.4 inches longer than on the 718 Boxster (111.8 inches vs. 97.4 inches).
For better handling and stability, the average track (width between the wheels) on the C-Class Cabriolet is 1.6 inches wider in the front and .6 inches wider in the rear than the average track on the 718 Boxster.
The C-Class Cabriolet’s front to rear weight distribution is more even (51.1% to 48.9%) than the 718 Boxster’s (45.5% to 54.5%). This gives the C-Class Cabriolet more stable handling and braking.
For better maneuverability, the C 300 Cabriolet’s turning circle is .7 feet tighter than the 718 Spyder’s (36.8 feet vs. 37.5 feet).
The design of the Mercedes C-Class Cabriolet amounts to more than styling. The C-Class Cabriolet has an aerodynamic coefficient of drag of .3 Cd. That is lower than the 718 Boxster (.31 to .34) and many sports cars. A more efficient exterior helps keep the interior quieter and helps the C-Class Cabriolet get better fuel mileage.
The front grille of the C-Class Cabriolet uses electronically controlled shutters to close off airflow and reduce drag when less engine cooling is needed. This helps improve highway fuel economy. The 718 Boxster doesn’t offer active grille shutters.
The C-Class Cabriolet has standard seating for 4 passengers; the 718 Boxster can only carry 2.
The C-Class Cabriolet has 32.3 cubic feet more passenger volume than the 718 Boxster (81.3 vs. 49).
With its convertible body style, locking rear seatbacks and remote trunk release lockout, the C-Class offers cargo security. The 718 Boxster’s non-lockable remote release defeats cargo security.
The C-Class Cabriolet has a standard remote vehicle starting system, so the vehicle can be started from inside the driver's house. This allows the driver to comfortably warm up the engine before going out to the vehicle. The climate system will also automatically heat or cool the interior. The 718 Boxster doesn’t offer a remote starting system.
Unlike the driver-only memory system optional at extra cost in the 718 Boxster, the C-Class Cabriolet offers an optional passenger memory, so that when drivers switch, the memory setting adjusts the driver’s seat, steering wheel position and outside mirror angle and the front passenger seat also adjusts to the new passenger’s preset preferences.
The C-Class Cabriolet’s standard easy entry system raises the steering wheel, making it easier for the driver to get in and out. An easy entry system costs extra on the 718 Boxster.
The C-Class Cabriolet offers an optional heads-up display that projects speed and navigation instruction readouts in front of the driver’s line of sight, allowing drivers to view information without diverting their eyes from the road. The 718 Boxster doesn’t offer a heads-up display.
The C-Class Cabriolet’s standard power windows have a locking feature to keep children in the rear seat from operating them, but the driver can still raise and lower all of them with the lock engaged. Porsche does not offer a locking feature on the 718 Boxster’s standard power windows.
If the windows are left open on the C-Class Cabriolet the driver can close them all at the outside door handle or from a distance using the remote. On a hot day the driver can lower the windows from a distance using the keyless remote. The driver of the 718 Boxster can only operate the windows from inside the vehicle, with the ignition on.
The C-Class Cabriolet’s power window, power lock, power mirror and cruise control switches are lit from behind, making them plainly visible and easier to operate at night. The 718 Boxster’s cruise control switches are unlit, making them difficult to find at night and operate safely.
The C-Class Cabriolet’s rain-sensitive wipers adjust their speed and turn on and off automatically based on the amount of rainfall on the windshield. This allows the driver to concentrate on driving without constantly adjusting the wipers. The 718 Boxster’s standard manually variable intermittent wipers have to be constantly adjusted.
To shield the driver and front passenger’s vision over a larger portion of the windshield and side windows, the C-Class Cabriolet has standard extendable sun visors. The 718 Boxster doesn’t offer extendable visors.
The C-Class Cabriolet’s sun-visors swivel front-to-side to block glare from the side windows. The 718 Boxster’s visors are fixed into the windshield header.
The C-Class Cabriolet has a standard dual zone air conditioning allows the driver and front passenger to choose two completely different temperatures so people with different temperature preferences won’t have to compromise. This makes both the driver and front passenger as comfortable as possible. Dual zone air conditioning costs extra on the 718 Boxster.
The C-Class Cabriolet’s optional Active Parking Assist can parallel park or back into a parking spot by itself, stopping and changing direction automatically. The 718 Boxster doesn’t offer an automated parking system.
The Mercedes C-Class comes in coupe, convertible and sedan bodystyles; the Porsche 718 isn’t available as a sedan.
Consumer Reports® recommends both the Mercedes C-Class Cabriolet and the Porsche 718 Boxster, based on reliability, safety and performance.
J.D. Power and Associates rated the C-Class Cabriolet first among compact premium cars in owner reported satisfaction. This includes how well the vehicle performs and satisfies its owner’s expectations. The 718 Boxster isn’t in the top three.
The Mercedes C-Class outsold the Porsche 718 by over 13 to one during the 2019 model year.
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