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The SL’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The 911 doesn’t offer pre-crash pretensioners.
The SL has standard NECK-PRO Head Restraints, which use a specially designed headrest to protect the driver and front passenger from whiplash. During a rear-end collision, the NECK-PRO Head Restraints system moves the headrests forward to prevent neck and spine injuries. The 911 doesn’t offer a whiplash protection system.
An active infrared night vision system optional on the SL helps the driver to more easily detect people, animals or other objects in front of the vehicle at night. Using an infrared camera and near-infrared lights to detect heat, the system then displays the image on a monitor in the dashboard. The 911 doesn’t offer a night vision system.
The SL’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 911 doesn’t offer a lane departure warning system.
The SL’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 911 doesn’t offer a driver alert monitor.
Both the SL and the 911 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, rearview cameras and available blind spot warning systems.
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 SL’s warranty.
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 SL has more powerful engines than the 911:
SL 450 3.0 turbo V6
SL 550 4.7 turbo V8
911 3.0 turbo 6 cyl.
911 S 3.0 turbo 6 cyl.
911 GTS 3.0 turbo 6 cyl.
911 GT3 4.0 DOHC 6 cyl.
911 GT3 RS 4.0 DOHC 6 cyl.
The SL has 2.9 gallons more fuel capacity than the 911 RWD’s standard fuel tank (19.8 vs. 16.9 gallons), for longer range between fill-ups.
In its Green Vehicle Guide, the U.S. Environmental Protection Agency (EPA) rates the Mercedes SL higher (3 out of 10) than the Porsche 911 (1). This means the SL produces up to 22.5 pounds less smog-producing pollutants than the 911 every 15,000 miles.
The Mercedes SL comes standard with an automatic transmission, for driver comfort, especially in the city. Automatic costs extra on the 911.
A nine-speed automatic is standard on the Mercedes SL, for better acceleration and lower engine speed on the highway. Only a seven-speed automatic is available for the 911.
For better stopping power the SL’s standard front brake rotors are larger than those on the 911:
For better traction, the SL has larger front tires than the 911 (255/35R19 vs. 235/40R19).
The SL’s 255/35R19 front and 285/30R19 rear tires provide better handling because they have a lower 35 series front and 30 series rear profile (height to width ratio) that provides a stiffer sidewall than the 911’s standard 40 series front and 35 series rear tires.
The SL offers an available adjustable active suspension system, which counteracts cornering forces actively, limiting body roll and improving handling and stability. Porsche doesn’t offer an active suspension on the 911.
For a smoother ride and more stable handling, the SL’s wheelbase is 5.3 inches longer than on the 911 (101.8 inches vs. 96.5 inches).
For better handling and stability, the track (width between the wheels) on the SL is 1.8 inches wider in the front and 1.8 inches wider in the rear than the average track on the 911.
The SL’s standard power retractable hardtop allows a seamless transition from an open car, to a completely sealed coupe. The 911 doesn’t offer a retractable hardtop.
The SL has a much larger trunk with its top down than the 911 Cabriolet (8.5 vs. 5.1 cubic feet).
With its convertible body style, valet key and remote trunk release lockout, the SL offers cargo security. The 911’s non-lockable folding seat and non-lockable remote release defeat cargo security.
To make loading groceries and cargo easier when your hands are full, the SL’s trunk can be opened and closed just by kicking your foot under the back bumper, leaving your hands completely free. The 911 doesn’t offer a hands-free gesture to open its trunk, forcing you to put cargo down if your hands are full.
The SL 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 911 doesn’t offer a remote starting system.
Unlike the driver-only memory system optional at extra cost in the 911, the SL has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver’s seat, steering wheel position, outside mirror angle and climate settings and the front passenger seat also adjusts to the new passenger’s preset preferences.
The SL’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 911.
If the windows are left open on the SL the driver can close them all at the outside door handle or from a distance using the remote (remote must be aimed at door sensor). On a hot day the driver can also lower the windows the same way. The driver of the 911 can only operate the windows from inside the vehicle, with the ignition on.
In case of a sudden change of weather, the SL has a standard remote convertible top that can be raised from a distance to protect the interior of the vehicle from damage. The 911 doesn’t offer a remote top, so the driver will have to run to the car, get in, turn the ignition on and raise the top to prevent the interior from being damaged.
Keyless-Go standard on the SL allows you to unlock the driver’s door, trunk and start the engine all without removing a key from pocket or purse. This eliminates searching for keys before loading groceries, getting in the vehicle in bad weather or making a hurried start to your trip. The Porsche 911’s available Porsche Entry and Drive doesn’t unlock the trunk.
Heated windshield washer fluid is standard on the SL to defrost the washer nozzles and quickly clear ice and frost from the windshield without scraping. The 911 doesn’t offer heated windshield washer fluid.
To shield the driver and front passenger’s vision over a larger portion of the windshield and side windows, the SL has standard extendable sun visors. The 911 doesn’t offer extendable visors.
The SL’s optional Active Parking Assist can parallel park or back into a parking spot by itself. The 911 doesn’t offer an automated parking system.
Insurance will cost less for the SL owner. The Complete Car Cost Guide estimates that insurance for the SL will cost $6165 to $8310 less than the 911 over a five-year period.
IntelliChoice estimates that five-year ownership costs (depreciation, financing, insurance, fuel, fees, repairs and maintenance) for the Mercedes SL will be $23344 to $45871 less than for the Porsche 911.
© 1991-2018 Advanta-STAR Automotive Research. All rights reserved.
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