2018 Audi A8 vs. 2018 Cadillac CT6

Detailed Review, Specifications & Comparison

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Both the A8 and CT6 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 CT6’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 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 CT6 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 CT6.

Both the A8 and the CT6 have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front seatbelt pretensioners, height adjustable front shoulder belts, plastic fuel tanks, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras, available crash mitigating brakes, night vision systems, lane departure warning systems, blind spot warning systems and around view monitors.


The A8’s corrosion warranty is 6 years longer than the CT6’s (12 vs. 6 years).


J.D. Power and Associates’ 2016 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that Audi vehicles are more reliable than Cadillac vehicles. J.D. Power ranks Audi 11th in reliability, above the industry average. With 11 more problems per 100 vehicles, Cadillac is ranked 15th.

From surveys of all its subscribers, Consumer Reports’ April 2017 Auto Issue reports that Audi vehicle are more reliable than Cadillac vehicles. Consumer Reports ranks Audi fourth in reliability. Cadillac is ranked 21st.


The A8 has more powerful engines than the CT6:




A8 3.0T 3.0 supercharged V6

333 HP

325 lbs.-ft.

A8 4.0T 4.0 turbo V8

450 HP

444 lbs.-ft.

CT6 2.0 turbo 4 cyl.

265 HP

295 lbs.-ft.

CT6 3.6 DOHC V6

335 HP

285 lbs.-ft.

CT6 3.0 turbo V6

404 HP

400 lbs.-ft.

As tested in Car and Driver the A8 4.0T 4.0 turbo V8 is faster than the Cadillac CT6 twin turbo V6:




Zero to 60 MPH

3.9 sec

5 sec

Zero to 100 MPH

9.8 sec

12.2 sec

5 to 60 MPH Rolling Start

5 sec

6.7 sec

Quarter Mile

12.4 sec

13.5 sec

Speed in 1/4 Mile

112 MPH

105 MPH

Fuel Economy and Range

On the EPA test cycle the A8 3.0T gets better fuel mileage than the CT6 AWD turbo V6 (19 city/29 hwy vs. 18 city/26 hwy).

Regenerative brakes improve the A8’s fuel efficiency by converting inertia back into energy instead of wasting it. The CT6 doesn’t offer a regenerative braking system.

The A8 has 2.5 gallons more fuel capacity than the CT6 (21.7 vs. 19.2 gallons), for longer range between fill-ups.


The A8 offers an available sequential manual gearbox (SMG). With no clutch pedal to worry about and a fully automatic mode, an SMG is much more efficient than a conventional automatic but just as easy to drive. The CT6 doesn’t offer an SMG or a conventional manual transmission.

Brakes and Stopping

For better stopping power the A8’s brake rotors are larger than those on the CT6:



CT6 2.0


Front Rotors

15 inches

12.6 inches

13.6 inches

Rear Rotors

14 inches

12.4 inches

12.4 inches

The A8 stops shorter than the CT6:





70 to 0 MPH

159 feet

164 feet

Car and Driver

Tires and Wheels

For better traction, the A8 has larger standard tires than the CT6 (255/45R19 vs. 235/50R18). The A8’s optional tires are larger than the largest tires available on the CT6 (275/35R21 vs. 245/45R19).

The A8’s standard tires provide better handling because they have a lower 45 series profile (height to width ratio) that provides a stiffer sidewall than the CT6’s standard 50 series tires. The A8’s optional tires have a lower 35 series profile than the CT6’s optional 40 series tires.

For better ride, handling and brake cooling the A8 has standard 19-inch wheels. Smaller 18-inch wheels are standard on the CT6. The A8’s optional 21-inch wheels are larger than the 20-inch wheels optional on the CT6.

Suspension and Handling

The front and rear suspension of the A8 uses air springs for a smoother, controlled ride than the CT6, which uses coil springs. Air springs maintain proper ride height and ride more smoothly.

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 CT6 doesn’t offer a load leveling suspension.

For better handling and stability, the track (width between the wheels) on the A8 is 1.4 inches wider in the front and .4 inches wider in the rear than on the CT6.

The A8 4.0T handles at .86 G’s, while the CT6 pulls only .81 G’s of cornering force in a Car and Driver skidpad test.


As tested by Car and Driver, the interior of the A8 4.0T is quieter than the CT6 AWD:




At idle

36 dB

49 dB


71 dB

73 dB

Passenger Space

The A8 has .9 inches more front shoulder room, 1.1 inches more rear headroom, 2.5 inches more rear legroom and 1.6 inches more rear shoulder room than the CT6.

Cargo Capacity

A low lift-over trunk design makes loading and unloading the A8 easier. The A8’s trunk lift-over height is 27.2 inches, while the CT6’s liftover is 29.1 inches.

A standard locking glovebox (which can’t be accessed with the valet key) keeps your small valuables safer in the A8. The CT6 doesn’t offer locking storage for small valuables.


If the windows are left down on the A8 the driver can raise them all using the key in the outside lock cylinder; on a hot day the driver can lower the windows. The driver of the CT6 can only raise the windows from inside the vehicle, with the ignition on.

The A8’s rain-sensitive wipers adjust their speed and turn on and off automatically based on the amount of rainfall on the windshield. This allows the driver to concentrate on driving without constantly adjusting the wipers. The CT6’s intermittent wipers change speed with vehicle speed, but can’t turn on and off or change speed based on changing rainfall.

Heated windshield washer nozzles are standard on the A8 to prevent washer fluid and nozzles from freezing and help continue to keep the windshield clear in sub-freezing temperatures. The CT6 doesn’t offer heated windshield washer nozzles.

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 CT6 doesn’t offer headlight washers.

The CT6 Luxury/Premium/Platinum’s cornering lamps activate a lamp on the front corner when the turn signal is activated. The A8’s standard adaptive cornering lights turn the actual headlight unit up to several degrees, depending on steering wheel angle and vehicle speed. This lights a significant distance into corners at any speed.

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

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