2019 Mercedes S-Class vs. 2019 Acura RLX

Detailed Review, Specifications & Comparison

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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 Acura RLX 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 RLX doesn’t offer inflatable seatbelts.

An active infrared night vision system optional on the S-Class 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 RLX doesn’t offer a night vision system.

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 RLX doesn’t offer a driver alert monitor.

Both the S-Class and the RLX have standard driver and passenger frontal airbags, front 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, crash mitigating brakes, daytime running lights, lane departure warning systems, blind spot warning systems, rearview cameras, available all wheel drive, around view monitors and rear cross-path warning.


There are over 41 percent more Mercedes dealers than there are Acura dealers, which makes it easier should you ever need service under the S-Class’ warranty.


A reliable vehicle saves its owner time, money and trouble. Nobody wants to be stranded or have to be without a vehicle while it’s being repaired. Consumer Reports rates the S-Class’ reliability 15 points higher than the RLX.

J.D. Power and Associates rated the S-Class third among large premium cars in their 2018 Initial Quality Study. The RLX isn’t in the top three.

J.D. Power and Associates’ 2018 Initial Quality Study of new car owners surveyed provide the statistics that show that Mercedes vehicles are better in initial quality than Acura vehicles. J.D. Power ranks Mercedes 14th in initial quality, above the industry average. With 7 more problems per 100 vehicles, Acura is ranked 20th, below the industry average.

J.D. Power and Associates’ 2018 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that Mercedes vehicles are more reliable than Acura vehicles. J.D. Power ranks Mercedes 15th in reliability. With 12 more problems per 100 vehicles, Acura is ranked 20th.


The S-Class has more powerful engines than the RLX:




S 450 3.0 turbo V6

362 HP

369 lbs.-ft.

S 560 4.0 turbo V8

463 HP

516 lbs.-ft.

AMG S 63 4.0 turbo V8

603 HP

664 lbs.-ft.

AMG S 65/Maybach S 650 6.0 turbo V12

621 HP

738 lbs.-ft.


310 HP

272 lbs.-ft.

RLX Sport Hybrid 3.5 SOHC V6

377 HP

341 lbs.-ft.

Fuel Economy and Range

Regardless of its engine, the S-Class’ engine automatically turns off when the vehicle is stopped, saving fuel and reducing pollution. (Start/Stop isn’t accounted in present EPA fuel mileage tests.) Acura only offers an automatic engine start/stop system on the RLX Sport Hybrid.

The S-Class’ standard fuel tank has 6 gallons more fuel capacity than the RLX Sport Hybrid’s standard fuel tank (21.1 vs. 15.1 gallons), for longer range between fill-ups. The S-Class V12’s standard fuel tank has 6.1 gallons more fuel capacity than the RLX’s standard fuel tank (24.6 vs. 18.5 gallons).


The S-Class 63/65’s launch control uses engine electronics to hold engine RPM’s precisely in order to provide the most stable and rapid acceleration possible, using all of the available traction. The RLX doesn’t offer launch control.

Brakes and Stopping

For better stopping power the S-Class’ brake rotors are larger than those on the RLX:


S 450/560

S 63/65


RLX Sport Hybrid

Front Rotors

14.6 inches

16.5 inches

12.3 inches

13 inches

Rear Rotors

14.2 inches

14.2 inches

12.2 inches

12.2 inches

The S-Class’ standard front and rear disc brakes are vented to help dissipate heat for shorter stops with less fading. The rear discs on the RLX are solid, not vented.

The S-Class S 63/65 offers optional heat-treated ceramic brake rotors, which last ten to twenty times as long as conventional cast iron rotors, don’t rust, don’t fade during repeated high speed braking, and their lighter weight contribute to better braking, handling and acceleration. The RLX doesn’t offer ceramic brake rotors.

The S-Class stops shorter than the RLX:





60 to 0 MPH

114 feet

119 feet

Motor Trend

Tires and Wheels

For better traction, the S 63’s tires are larger than the largest tires available on the RLX (F:255/40R20 & R:285/35R20 vs. 245/40R19).

The S 63’s 285/35R20 rear tires provide better handling because they have a lower 35 series profile (height to width ratio) that provides a stiffer sidewall than the RLX’s 40 series tires.

For better ride, handling and brake cooling the S 63 has standard 20-inch wheels. The RLX’s largest wheels are only 19-inches.

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 RLX doesn’t offer run-flat tires.

Suspension and Handling

The front and rear suspension of the S-Class uses air springs for a smoother, controlled ride than the RLX, which uses coil springs. Air springs maintain proper ride height and ride more smoothly.

The S-Class offers an available adjustable active suspension system, which counteracts cornering forces actively, limiting body roll and improving handling and stability. Acura doesn’t offer an active suspension on the RLX.

The S-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 RLX’s suspension doesn’t offer adjustable shock absorbers.

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

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 RLX doesn’t offer drift compensation steering.

For a smoother ride and more stable handling, the S-Class’ wheelbase is 12.4 inches longer than on the RLX (124.6 inches vs. 112.2 inches). The Maybach S-Class’ wheelbase is 20.3 inches longer than on the RLX (132.5 inches vs. 112.2 inches).

The S 600 handles at .90 G’s, while the RLX pulls only .80 G’s of cornering force in a Motor Trend skidpad test.

The S 600 executes Motor Trend’s “Figure Eight” maneuver 1.5 seconds quicker than the RLX (25.8 seconds @ .75 average G’s vs. 27.3 seconds @ .64 average G’s).

For better maneuverability, the S AMG S 65’s turning circle is 2.4 feet tighter than the RLX’s (38.1 feet vs. 40.5 feet). The S 450/560’s turning circle is .1 feet tighter than the RLX’s (40.4 feet vs. 40.5 feet).

Passenger Space

Because it has more passenger and cargo room, the EPA rates the S-Class a Large car, while the RLX is rated a Mid-size.

The S-Class has 9.9 cubic feet more passenger volume than the RLX (112 vs. 102.1).

The S-Class has 2.1 inches more front headroom, .1 inches more front shoulder room, .5 inches more rear headroom and 2.1 inches more rear shoulder room than the RLX.

For enhanced passenger comfort on long trips the S-Class’ available rear seats recline. The RLX’s rear seats don’t recline.

Cargo Capacity

The S-Class has a much larger trunk than the RLX (16.3 vs. 14.9 cubic feet). The S-Class has a much larger trunk than the RLX Sport Hybrid (16.3 vs. 11.6 cubic feet).

To make loading and unloading groceries and cargo easier, especially for short adults, the S-Class has a standard power trunk, which opens and closes automatically by pressing a button, or optionally by just kicking your foot under the back bumper, completely leaving your hands free. The RLX doesn’t offer a power trunk.

Servicing Ease

The engine in the S-Class is mounted longitudinally (North-South), instead of sideways, as in the RLX. This makes it easier to service and maintain, because there are no rear spark plugs and the accessory belts are in front.

J.D. Power and Associates surveys of service recipients show that Mercedes service is better than Acura. J.D. Power ranks Mercedes 6th in service department satisfaction (above the industry average). With a 23% lower rating, Acura is ranked 12th.


Unlike the driver-only memory system in the RLX, the S-Class has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver’s seat, steering wheel position and outside mirror angle and the front passenger seat also adjusts to the new passenger’s preset preferences.

The power windows standard on both the S-Class and the RLX have locks to prevent small children from operating them. When the lock on the S-Class is engaged the driver can still operate all of the windows, for instance to close one opened by a child. The RLX prevents the driver from operating the other windows just as it does the other passengers.

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 RLX doesn’t offer heated windshield washer fluid.

To help drivers see further while navigating curves, the S-Class has standard adaptive headlights to illuminate around corners automatically by reading vehicle speed and steering wheel angle. The RLX doesn’t offer cornering lights.

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 RLX doesn’t offer secondary sun visors.

Optional air conditioned front and rear seats keep the S-Class’ passengers comfortable and take the sting out of hot leather in summer. The RLX doesn’t offer air-conditioned seats in the rear.

To quickly and conveniently keep personal devices charged without cables tangling and wearing out, the Mercedes S-Class has a standard wireless phone charging system (Qi) in the center console and for the rear passengers. The RLX doesn’t offer wireless personal charging.

To quickly and conveniently keep personal devices charged without cables tangling and wearing out, the Mercedes S-Class has a standard wireless phone charging system (Qi) in the center console and for the rear passengers. The RLX doesn’t offer wireless personal charging.

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 RLX 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 RLX doesn’t offer an automated parking system.

Model Availability

The Mercedes S-Class comes in coupe, convertible and sedan bodystyles; the Acura RLX isn’t available as a coupe or convertible.


Consumer Reports® recommends the Mercedes S-Class, based on reliability, safety and performance. The Acura RLX isn't recommended.

The Mercedes S-Class outsold the Acura RLX by over 8 to one during the 2018 model year.

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

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