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Both the A8 and RLX have child safety locks to prevent children from opening the rear doors. The A8 has power child safety locks, allowing the driver to activate and deactivate them from the driver's seat and to know when they're engaged. The RLX’s child locks have to be individually engaged at each rear door with a manual switch. The driver can’t know the status of the locks without opening the doors and checking them.
The A8 has a standard front seat center airbag, which deploys between the driver and front passenger, protecting them from injuries caused by striking each other in serious side impacts. The RLX doesn’t offer front seat center airbags.
The A8 has a standard Secondary Collision Brake Assist, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The RLX doesn’t offer a post collision braking system: in the event of a collision that triggers the airbags, more collisions are possible without the protection of airbags that may have already deployed.
To provide maximum traction and stability on all roads, All-Wheel Drive is standard on the A8. But it costs extra on the RLX.
A passive infrared night vision system optional on the A8 TFSI 60 helps the driver to more easily detect people, animals or other objects in front of the vehicle at night. Using an infrared camera to detect heat, the system then displays the image on a monitor in the dashboard and even aims one of the vehicle’s headlights in the direction of the person or object. The RLX doesn’t offer a night vision system.
Both the A8 and the RLX have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, front seatbelt pretensioners, 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, rearview cameras, available blind spot warning systems, around view monitors and rear cross-path warning.
The A8’s corrosion warranty is 7 years longer than the RLX’s (12 vs. 5 years).
There are over 11 percent more Audi dealers than there are Acura dealers, which makes it easier should you ever need service under the A8’s warranty.
A hardened steel chain, with no maintenance needs, drives the camshafts in the A8’s engine. A rubber cam drive belt that needs periodic replacement drives the RLX’s camshafts. If the RLX’s belt breaks, the engine could be severely damaged when the pistons hit the opened valves.
J.D. Power and Associates’ 2019 Initial Quality Study of new car owners surveyed provide the statistics that show that Audi vehicles are better in initial quality than Acura vehicles. J.D. Power ranks Audi 22nd in initial quality. With 4 more problems per 100 vehicles, Acura is ranked 24th.
J.D. Power and Associates’ 2019 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that Audi vehicles are more reliable than Acura vehicles. J.D. Power ranks Audi 8th in reliability, above the industry average. With 47 more problems per 100 vehicles, Acura is ranked 26th.
From surveys of all its subscribers, Consumer Reports’ December 2018 Auto Issue reports that Audi vehicles are more reliable than Acura vehicles. Consumer Reports ranks Audi 6 places higher in reliability than Acura.
The A8 55 TSFI’s standard 3.0 turbo V6 hybrid produces 25 more horsepower (335 vs. 310) and 97 lbs.-ft. more torque (369 vs. 272) than the RLX’s standard 3.5 SOHC V6. The A8 55 TSFI’s 3.0 turbo V6 hybrid produces 28 lbs.-ft. more torque (369 vs. 341) than the RLX Sport Hybrid’s standard 3.5 SOHC V6 hybrid. The A8 60 TFSI’s standard 4.0 turbo V8 hybrid produces 76 more horsepower (453 vs. 377) and 146 lbs.-ft. more torque (487 vs. 341) than the RLX Sport Hybrid’s standard 3.5 SOHC V6 hybrid.
The A8 has 6.6 gallons more fuel capacity than the RLX Sport Hybrid’s standard fuel tank (21.7 vs. 15.1 gallons), for longer range between fill-ups. The A8 has 3.2 gallons more fuel capacity than the RLX’s standard fuel tank (21.7 vs. 18.5 gallons).
For better stopping power the A8’s brake rotors are larger than those on the RLX:
A8 55 TSFI
A8 60 TFSI
RLX Sport Hybrid
The A8’s 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 A8 stops much shorter than the RLX:
70 to 0 MPH
Car and Driver
For better traction, the A8 has larger standard tires than the RLX (255/45R19 vs. 245/40R19). The A8’s optional tires are larger than the largest tires available on the RLX (265/40R20 vs. 245/40R19).
For better ride, handling and brake cooling the A8 offers optional 20-inch wheels. The RLX’s largest wheels are only 19-inches.
The A8 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 RLX; it requires you to depend on roadside assistance and your vehicle will have to be towed.
The front and rear suspension of the A8 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 A8 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 A8 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 A8 has a standard automatic front and rear load leveling suspension to keep ride height level with a heavy load or when towing. The A8’s height leveling suspension allows the driver to raise ride height for better off-road clearance and then lower it again for easier entering and exiting and better on-road handling. The RLX doesn’t offer a load leveling suspension.
For a smoother ride and more stable handling, the A8’s wheelbase is 10.9 inches longer than on the RLX (123.1 inches vs. 112.2 inches).
The A8 55 TSFI handles at .93 G’s, while the RLX pulls only .84 G’s of cornering force in a Car and Driver skidpad test.
The A8 has .7 inches more front headroom, 1.6 inches more rear headroom, 5.5 inches more rear legroom and .6 inches more rear shoulder room than the RLX.
For enhanced passenger comfort on long trips the A8’s available rear seats recline. The RLX’s rear seats don’t recline.
To make loading and unloading groceries and cargo easier when your hands are full, the A8’s power trunk can be opened or closed just by kicking your foot under the back bumper, leaving your hands completely free. The RLX doesn’t offer a power or hands-free opening trunk.
The A8 has a 3500 lbs. towing capacity. The RLX has no towing capacity.
The engine in the A8 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.
Unlike the driver-only memory system in the RLX, the A8 has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver’s seat, steering wheel position, outside mirror angle and climate settings and the front passenger seat also adjusts to the new passenger’s preset preferences.
The power windows standard on both the A8 and the RLX have locks to prevent small children from operating them. When the lock on the A8 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.
In poor weather, headlights can lose their effectiveness as grime builds up on their lenses. This can reduce visibility without the driver realizing. The A8 has standard headlight washers to keep headlight output high. The RLX doesn’t offer headlight washers.
To help drivers see further while navigating curves, the A8 offers optional adaptive headlights to illuminate around corners automatically by reading vehicle speed and steering wheel angle. The RLX doesn’t offer cornering lights.
Optional air conditioned front and rear seats keep the A8’s 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 Audi A8 offers an optional wireless phone charging system (Qi) in the center console. The RLX doesn’t offer wireless personal charging.
The A8 offers an optional 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.
Consumer Reports® recommends the Audi A8, based on reliability, safety and performance. The Acura RLX isn't recommended.
The Audi A8/S8 outsold the Acura RLX by over two to one during the 2019 model year.
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