Certified Benz & Beemer Compares 2003 Mercedes Benz SL-Class VS 2003 Porsche 911 Near Phoenix, AZ

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2003 Mercedes Benz SL-Class

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2003 Porsche 911

Safety Comparison

For enhanced safety, the front seat shoulder belts of the Mercedes SL Class are height adjustable to accommodate a wide variety of driver and passenger heights. A better fit can prevent injuries and the increased comfort also encourages passengers to buckle up. The Porsche 911 doesn’t offer height adjustable seat belts.

Using vehicle speed sensors, smart airbags in the SL Class deploy with different levels of force to help better protect passengers of all sizes in different collisions. The 911’s airbags don’t have smart features and will always deploy full force.

The Mercedes SL Class has Daytime Running Lights to help keep it more visible under all conditions. Daytime Running Lights decrease the chances of collisions. Canadian government studies show that driving with lights during the day reduces accidents by 11% by making vehicles more conspicuous. The 911 doesn’t offer Daytime Running Lights.

The SL Class has standard Tele Aid, which uses a global positioning satellite (GPS) receiver and a cellular system to get driving directions, remotely unlock your doors if you lock your keys in, help track down your vehicle if it’s stolen or send emergency personnel to the scene if any airbags deploy. The 911 doesn’t offer a GPS response system, only a navigation computer with no live response for emergencies.

Both the SL Class and the 911 have standard driver and passenger frontal airbags, front side-impact airbags, head airbags, front seatbelt pretensioners and four wheel antilock brakes.

The Mercedes SL Class weighs 657 to 1276 pounds more than the Porsche 911. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.

Warranty Comparison

Mercedes pays for scheduled maintenance on the SL Class for 4 years and 50,000 miles. Mercedes will pay for oil changes, tire rotation, lubrication and any other scheduled maintenance. Porsche doesn’t pay scheduled maintenance for the 911.

There are over 60 percent more Mercedes dealers than there are Porsche dealers, which makes it much easier to get service under the SL Class’ warranty.

Reliability Comparison

The engines in the SL Class have a single overhead cam for simplicity. The engines in the 911 have dual overhead cams, which add to the number of moving parts and the complexity of the cylinder heads.

J.D. Power and Associates’ surveys of new car owners provide the statistics that show that Mercedes vehicles are better in initial quality than Porsche vehicles. J.D. Power ranks Mercedes 10th in initial quality, above the industry average. With 11 more problems per 100 vehicles, Porsche is ranked 14th.

Engine Comparison

The SL Class has more powerful engines than the 911:



SL500 5.0 SOHC V8

302 HP

339 lbs.-ft.

SL55 AMG 5.4 supercharged SOHC V8

493 HP

516 lbs.-ft.

911 3.6 DOHC 6 cyl.

315 HP

273 lbs.-ft.

911 Turbo 3.6 turbo DOHC 6 cyl.

415 HP

415 lbs.-ft.

911 Turbo 3.6 turbo DOHC 6 cyl.

450 HP

457 lbs.-ft.

GT2 3.6 turbo DOHC 6 cyl.

456 HP

457 lbs.-ft.

For more instantaneous acceleration and better engine flexibility in any gear, the SL Class’ engines produce their peak torque at lower RPM’s than the 911:


SL500 5.0 SOHC V8

2700 RPM

SL55 AMG 5.4 supercharged SOHC V8

2650 RPM

911 3.6 DOHC 6 cyl.

4250 RPM

911 Turbo 3.6 turbo DOHC 6 cyl.

2700 RPM

911 Turbo 3.6 turbo DOHC 6 cyl.

3500 RPM

GT2 3.6 turbo DOHC 6 cyl.

3500 RPM

Fuel Economy and Range Comparison

The SL Class’ standard fuel tank has 4.2 gallons more fuel capacity than the 911 (21.1 vs. 16.9 gallons), for longer range between fill ups. The SL Class AMG’s 24 gallon tank has 7.1 gallons more capacity than the 911.

Brakes and Stopping Comparison

For better stopping power the SL Class’ brake rotors are larger than those on the 911:

SL Class




Front Rotors

12.99 inches

14.17 inches

12.53 inches

13.8 inches

Rear Rotors

11.81 inches

13 inches

11.78 inches

13.8 inches

In an emergency stopping situation, many drivers don’t press the brakes with enough force to stop the vehicle in the shortest distance. Whatever factors cause this tendency, the SL Class has standard Brake Assist to detect emergency braking situations (by how hard and how quickly the brake pedal is pressed) and then automatically apply maximum braking immediately in order to help prevent a collision. The 911 doesn’t offer a brake assist feature.

The SL Class stops much shorter than the 911:

SL Class


80 to 0 MPH

205 feet

232 feet

Road & Track

70 to 0 MPH

155 feet

170 feet

Car and Driver

60 to 0 MPH

113 feet

126 feet


30 to 0 MPH

28 feet

33 feet


Tires and Wheels Comparison

For better traction, the SL Class has larger standard tires than the 911 (255/45R17 vs. 205/50R17). The SL Class’ optional front tires are larger than the largest tires available on the 911 (255/40R18 vs. 235/40R18).

The SL500’s standard tires provide better handling because they have a lower 45 series profile (height to width ratio) which provides a stiffer sidewall than the 911’s standard 50 series front tires.

Suspension and Handling Comparison

The SL Class 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.

The SL Class has a standard driver-adjustable suspension system. It allows the driver to choose between an extra-supple ride, reducing fatigue on long trips, or a sport setting, which allows maximum control for tricky roads. The 911’s suspension doesn’t offer adjustable shock absorbers.

The SL Class has a standard automatic front and rear load leveling suspension to keep ride height level with a heavy load or when towing. The 911 doesn’t offer a load leveling suspension.

For a smoother ride and more stable handling, the SL Class’ wheelbase is 8.2 inches longer than on the 911 (100.8 vs. 92.6 inches).

For better handling and stability, the average track (width between the wheels) on the SL Class is 3.9 inches wider in the front and 1.9 inches wider in the rear than the average track on the 911.

The SL Class’ front to rear weight distribution is more even (51% to 49%) than the 911’s (40% to 60%). This gives the SL Class more stable handling and braking.

The SL55 AMG handles at .91 G’s, while the 911 Cabriolet pulls only .86 G’s of cornering force in a Car and Driver skidpad test.

The SL500 goes through Road & Track’s slalom 3 MPH faster than the 911 Cabriolet Carrera 4 (67.6 vs. 64.6 MPH).

Chassis Comparison

The design of the Mercedes SL Class amounts to more than styling. The SL Class offers aerodynamic coefficients of drag from .29 to .3 Cd (depending on bodystyle and options). That is lower than the 911 (.31 to .34) and many sports cars. A more efficient exterior helps keep the interior quieter and helps the SL Class get better fuel mileage.

The SL Class’ 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.

As tested by Car and Driver, the interior of the SL500 is quieter than the 911 Turbo Carrera 4:

SL Class


At idle

46 dB

55 dB


78 dB

83 dB

70 MPH Cruising

70 dB

76 dB

70 MPH Coasting

70 dB

74 dB

Passenger Space Comparison

The SL Class has 1.3 inches more front legroom, 3.8 inches more front hip room and 2.3 inches more front shoulder room than the 911.

Cargo Capacity Comparison

The SL Class has a much larger trunk with its top up than the 911 Cabriolet with its top up (11.2 vs. 11.7 cubic feet).

With its sedan body style, remote release lock-out switch and remote trunk release lockout, the SL Class offers cargo security. The 911’s non-lockable folding seat defeats cargo security.

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