2019 BMW i8 vs. 2019 Mercedes SL

Detailed Review, Specifications & Comparison

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Safety

The i8 has all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The SL doesn’t offer all-wheel drive.

The i8 has a standard Surround View to allow the driver to see objects all around the vehicle on a screen. The SL only offers a rear monitor and front and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the sides.

Both the i8 and the SL 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.

Warranty

The i8’s corrosion warranty is 7 years longer than the SL’s (12 vs. 5 years).

BMW pays for scheduled maintenance on the i8 for 3 years and 36,000 miles. BMW will pay for oil changes, lubrication and any other required maintenance. Mercedes doesn’t pay scheduled maintenance for the SL.

Reliability

J.D. Power and Associates’ 2018 Initial Quality Study of new car owners surveyed provide the statistics that show that BMW vehicles are better in initial quality than Mercedes vehicles. J.D. Power ranks BMW 11th in initial quality, above the industry average. With 5 more problems per 100 vehicles, Mercedes is ranked 14th.

J.D. Power and Associates’ 2018 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that BMW vehicles are more reliable than Mercedes vehicles. J.D. Power ranks BMW 8th in reliability, above the industry average. With 20 more problems per 100 vehicles, Mercedes is ranked 15th.

From surveys of all its subscribers, Consumer Reports’ December 2018 Auto Issue reports that BMW vehicles are more reliable than Mercedes vehicles. Consumer Reports ranks BMW 9 places higher in reliability than Mercedes.

Engine

The i8’s 1.5 turbo 3 cyl. hybrid produces 7 more horsepower (369 vs. 362) and 51 lbs.-ft. more torque (420 vs. 369) than the SL 450’s standard 3.0 turbo V6.

As tested in Motor Trend the BMW i8 is faster than the SL 550:

 

i8

SL

Zero to 60 MPH

3.8 sec

4.1 sec

Quarter Mile

12.4 sec

12.5 sec

Fuel Economy and Range

On the EPA test cycle the i8 running on electricity gets better fuel mileage than the SL 450 (68 city/70 hwy MPGe vs. 20 city/28 hwy).

On the EPA test cycle the i8 running its gasoline engine gets better fuel mileage than the SL 450 (26 city/29 hwy vs. 20 city/28 hwy).

The i8 can drive on battery power alone for up to 18 miles. The SL must run its internal combustion engine to move.

Regenerative brakes improve the i8’s fuel efficiency by converting inertia back into energy instead of wasting it. The SL doesn’t offer a regenerative braking system.

Drivetrain

All wheel drive, available in the i8, 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 Mercedes SL is not available with all wheel drive.

Brakes and Stopping

The i8 stops shorter than the SL:

 

i8

SL

 

60 to 0 MPH

103 feet

109 feet

Motor Trend

Tires and Wheels

For better ride, handling and brake cooling the i8 has standard 20-inch wheels. Only 19-inch wheels are available on the SL.

Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires standard on the i8 can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The SL doesn’t offer run-flat tires.

Suspension and Handling

For a smoother ride and more stable handling, the i8’s wheelbase is 8.5 inches longer than on the SL (110.2 inches vs. 101.7 inches).

For better handling and stability, the track (width between the wheels) on the i8 is 1.4 inches wider in the front and 4.8 inches wider in the rear than the average track on the SL.

Chassis

The BMW i8 may be more efficient, handle and accelerate better because it weighs about 350 to 450 pounds less than the Mercedes SL.

The design of the BMW i8 amounts to more than styling. The i8 offers aerodynamic coefficients of drag from .27 to .28 Cd (depending on bodystyle and options). That is lower than the SL (.29 to .32). A more efficient exterior helps the i8 go faster and keeps the interior quieter. It also helps the i8 get better fuel mileage.

Passenger Space

The i8 Roadster has 4.2 cubic feet more passenger volume than the SL (54.7 vs. 50.5).

Ergonomics

The i8 has a standard heads-up display that projects speed and other key instrumentation readouts in front of the driver’s line of sight, allowing drivers to view information without diverting their eyes from the road. The SL doesn’t offer a heads-up display.

Model Availability

The BMW i8 comes in coupe and convertible bodystyles; the Mercedes SL isn’t available as a coupe.

Recommendations

The i8 was chosen as one of Automobile Magazine’s “All Stars” in 2015. The SL has never been an “All Star.”

© 1991-2018 Advanta-STAR Automotive Research. All rights reserved.

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