Both the SL Class and the 6 Series have standard driver and passenger frontal airbags, front side-impact airbags, head airbags, front seatbelt pretensioners, height adjustable front shoulder belts, four-wheel antilock brakes, traction control and electronic stability systems to prevent skidding.
The SL Class has more powerful engines than the 6 Series:
Horsepower |
Torque |
|
SL550 5.5 DOHC V8 |
382 HP |
391 lbs.-ft. |
SL55 AMG 5.4 supercharged V8 |
510 HP |
531 lbs.-ft. |
SL600 5.5 turbo V12 |
510 HP |
612 lbs.-ft. |
SL65 AMG 6.0 turbo V12 |
604 HP |
738 lbs.-ft. |
650i 4.8 DOHC V8 |
360 HP |
360 lbs.-ft. |
M6 Coupe 5.0 DOHC V10 |
500 HP |
383 lbs.-ft. |
As tested in Consumer Reports the SL550 5.5 DOHC V8 is faster than the 650i 4.8 DOHC V8 (automatics tested):
SL Class |
6 Series |
|
Zero to 30 MPH |
2 sec |
2.2 sec |
Zero to 60 MPH |
5.3 sec |
5.6 sec |
45 to 65 MPH Passing |
3.8 sec |
4 sec |
Quarter Mile |
13.8 sec |
14.1 sec |
Speed in 1/4 Mile |
104 MPH |
103 MPH |
For more instantaneous acceleration and better engine flexibility in any gear, the SL Class’ engines produce their peak torque and horsepower at lower RPM’s than the 6 Series:
Horsepower |
Torque |
|
SL550 5.5 DOHC V8 |
6000 RPM |
2800 RPM |
SL55 AMG 5.4 supercharged V8 |
6100 RPM |
2600 RPM |
SL600 5.5 turbo V12 |
5000 RPM |
3500 RPM |
SL65 AMG 6.0 turbo V12 |
5500 RPM |
2000 RPM |
650i 4.8 DOHC V8 |
6300 RPM |
3400 RPM |
M6 Coupe 5.0 DOHC V10 |
7750 RPM |
6100 RPM |
An engine control system, which can shut down half of the engine’s cylinders, helps improve the SL Class V12’s fuel efficiency. The 6 Series doesn’t offer a system that can shut down part of the engine.
The SL Class has 2.6 gallons more fuel capacity than the 6 Series (21.1 vs. 18.5 gallons), for longer range between fill-ups.
For better stopping power the SL65 AMG’s front brake rotors are larger than those on the 6 Series:
SL550 |
SL65 AMG |
6 Series |
M6 Coupe |
|
Front Rotors |
13.8 inches |
15.4 inches |
13.7 inches |
14.7 inches |
The SL Class stops shorter than the 6 Series:
SL Class |
6 Series |
||
80 to 0 MPH |
203 feet |
209 feet |
Road & Track |
70 to 0 MPH |
160 feet |
169 feet |
Car and Driver |
For better traction, the SL Class has larger tires than the 6 Series (F:255/40R18 & R:285/35R18 vs. F:245/45R18 & R:275/40R18).
The SL Class’ standard 255/40R18 front and 285/35R18 rear tires provide better handling because they have a lower 40 series front and 35 series rear profile (height to width ratio), which provides a stiffer sidewall than the 6 Series’ standard 45 series front and 40 series rear tires. The SL55/SL65’s 255/35R19 front and 285/30R19 rear tires have a lower 35 series front and 30 series rear profile than the 6 Series’ optional 40 series front and 35 series rear tires.
The SL Class has a standard 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 6 Series, it requires you to depend on its run-flat tires, which limits mileage and speed before they are repaired. If a run-flat is damaged beyond repair by a road hazard your vehicle will have to be towed. Some models of the 6 Series don’t even offer run-flats.
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 6 Series’ 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 6 Series doesn’t offer a load leveling suspension.
The SL65 AMG handles at .93 G’s, while the 6 Series Convertible pulls only .89 G’s of cornering force in a Car and Driver skidpad test.
The SL Class goes through Motor Trend’s slalom 2.9 MPH faster than the 6 Series Convertible (67.4 vs. 64.5 MPH).
The SL Class is 11.7 inches shorter than the 6 Series, making the SL Class easier to handle, maneuver and park in tight spaces.
The SL Class’ standard power retractable hardtop allows a seamless transition from an open car, to a completely sealed coupe. The 6 Series doesn't offer a retractable hardtop.
With its convertible body style, valet key and remote trunk release lockout, the SL Class offers cargo security. The 6 Series’ non-lockable remote release defeats cargo security.
Unlike the driver-only memory system in the 6 Series, the SL Class has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver’s seat, steering wheel position, seatbelt height, outside mirror angle and climate settings and the front passenger seat also adjusts to the new passenger’s preset preferences.
Consumer Reports rated the SL Class’ headlight performance “Very Good,” a higher rating than the 6 Series’ headlights, which were rated “Good.”
The SL Class’ optional air conditioned front seats cool the driver and front passenger and help take the sting out of hot leather in Summer. The 6 Series doesn’t offer air conditioned front seats.
© 1991-2016 Advanta-STAR Automotive Research. All rights reserved.
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