For enhanced safety, the front and rear seat shoulder belts of the Mercedes S-Class have pretensioners to tighten the seatbelts and eliminate dangerous slack in the event of a collision and force limiters to limit the pressure the belts will exert on the passengers. The Audi S8 doesn’t offer pretensioners for the rear seat belts.
The rear seatbelts optional on the S-Class inflate when a collision is detected, helping to spread crash forces over a much larger area of the body and limiting head and neck movement. This can help prevent spinal and internal injuries. The S8 doesn’t offer inflatable seatbelts.
The S-Class’ 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 S8 doesn’t offer a driver alert monitor.
The S-Class has standard mbrace, which uses a global positioning satellite (GPS) receiver and a cellular system to 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 S8 doesn’t offer a GPS response system, only a navigation computer with no live response for emergencies, so if you’re involved in an accident and you’re incapacitated help may not come as quickly.
Both the S-Class and the S8 have standard driver and passenger frontal airbags, front and rear side-impact airbags, driver knee airbags, side-impact head airbags, height adjustable front shoulder belts, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras, available night vision systems, lane departure warning systems, blind spot warning systems and around view monitors.
There are over 29 percent more Mercedes dealers than there are Audi dealers, which makes it easier should you ever need service under the S-Class’ warranty.
The S600’s standard 5.5 turbo V12 produces 59 lbs.-ft. more torque (612 vs. 553) than the S8’s 4.0 turbo V8. The S63 AMG’s standard 5.5 turbo V8 produces 111 lbs.-ft. more torque (664 vs. 553) than the S8’s 4.0 turbo V8. The S65 AMG’s standard 6.0 turbo V12 produces 16 more horsepower (621 vs. 605) and 185 lbs.-ft. more torque (738 vs. 553) than the S8’s 4.0 turbo V8.
On the EPA test cycle the S550e running on electricity gets better fuel mileage than the S8 (54 city/63 hwy MPGe vs. 15 city/24 hwy).
On the EPA test cycle the S550e running its gasoline engine gets better fuel mileage than the S8 (24 city/30 hwy vs. 15 city/24 hwy).
The S550e can drive on battery power alone for up to 18.6 miles. The S8 must run its internal combustion engine to move.
In heavy traffic or at stoplights the S-Class’ engine automatically turns off when the vehicle is stopped, saving fuel and reducing pollution. The engine is automatically restarted when the driver gets ready to move again. (Start/Stop isn’t accounted in present EPA fuel mileage tests.) The S8 doesn’t offer an automatic engine start/stop system.
The S-Class S63/S65/600’s standard fuel tank has 2.9 gallons more fuel capacity than the S8 (24.6 vs. 21.7 gallons).
Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires available on the S-Class can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The S8 doesn’t offer run-flat tires.
The S-Class offers an available active suspension system, which counteracts cornering forces actively, limiting body roll and improving handling and stability. Audi doesn’t offer an active suspension on the S8.
The S-Class’ 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 S8 doesn’t offer drift compensation steering.
For a smoother ride and more stable handling, the S-Class’ wheelbase is 6.7 inches longer than on the S8 (124.6 inches vs. 117.9 inches).
The S-Class’ front to rear weight distribution is more even (51.6% to 48.4%) than the S8’s (56.4% to 43.6%). This gives the S-Class more stable handling and braking.
For better maneuverability, the S65 AMG’s turning circle is 2.3 feet tighter than the S8’s (38.1 feet vs. 40.4 feet). The S550’s turning circle is .4 feet tighter than the S8’s (40 feet vs. 40.4 feet).
As tested by Car and Driver while at idle, the interior of the Maybach S600 is quieter than the S8 Plus (40 vs. 43 dB).
Because it has more passenger and cargo room, the S-Class is rated a Large car by the EPA, while the S8 is rated a Mid-size.
The S-Class has 10.1 cubic feet more passenger volume than the S8 (112 vs. 101.9).
The S-Class has 2.5 inches more front headroom, .6 inches more front shoulder room, 4.4 inches more rear legroom and 1.3 inches more rear shoulder room than the S8.
For enhanced passenger comfort on long trips the S-Class’ available rear seats recline. The S8’s rear seats don’t recline.
The S-Class has a much larger trunk than the S8 (16.3 vs. 14.2 cubic feet).
The S-Class 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 S8 doesn’t offer a remote starting system.
If the windows are left down on the S-Class the driver can raise them all using the key in the outside lock cylinder or the keyless remote; on a hot day the driver can lower the windows. The driver of the S8 can’t use the remote to operate the windows.
Heated windshield washer fluid is standard on the S-Class to defrost the washer nozzles and quickly clear ice and frost from the windshield without scraping. The S8 doesn’t offer heated windshield washer fluid. It’s standard heated washer nozzles will defrost the washer fluid but not the windshield.
To better shield the driver and front passenger’s vision, the S-Class has standard dual-element sun visors that can block glare from two directions simultaneously. The S8 doesn’t offer secondary sun visors.
When the S-Class is put in reverse, the passenger rearview mirror tilts from its original position. This gives the driver a better view of the curb during parallel parking maneuvers. Shifting out of reverse puts the mirror into its original position. The S8’s mirror doesn’t automatically adjust for backing.
Optional air conditioned front and rear seats keep the S-Class’ passengers comfortable and take the sting out of hot leather in Summer. The S8 doesn’t offer air-conditioned seats in the rear.
Optional Mercedes-Benz Apps for the S-Class allows the driver and passengers access to select programs on their smartphones, including reading text messages aloud, playing internet radio stations, finding fuel prices at nearby service stations, searching the internet and other connected activities without taking their eyes off the road or their hands from the wheel. The S8 doesn’t offer factory integrated smartphone program access.
The S-Class has a 115-volt a/c outlet on the center console, allowing you to recharge a laptop or run small household appliances without special adapters that can break or get misplaced. The S8 doesn’t offer a house-current electrical outlet.
The S-Class’ optional Active Parking Assist can parallel park or back into a parking spot by itself, with the driver only controlling speed with the brake pedal. The S8 doesn’t offer an automated parking system.
The S-Class is ranked first in its class and received the 2015 “Total Quality Award.” The S8 is not ranked.
The S-Class was chosen as one of Automobile Magazine’s “All Stars” for 3 of the last 18 years. The A8 hasn’t been picked since 2005.
The Mercedes S-Class outsold the Audi A8/S8 by almost five to one during the 2016 model year.