Audi S6
Biturbo V8 with 309 kW for S6/S7 C7 and S8 D4. Detuned version of the RS V8 with cylinder deactivation. Comfortable and powerful at the same time.
Last V8-powered S6 — the community knows, prices are rising
420 hp twin-turbo V8, honey-smooth and brutal at the same time. The last S6 with eight cylinders — PistonHeads calls it 'last chance to get a V8'. Used prices climbing since the C8 only offers a V6. Cold start sounds like a subtle thunderclap. Running costs are real, but so is the character.
Engine Weaknesses 10
KBA recall (code 21H7) for S6 and RS6 built June 2012 to March 2017: the too-fine oil strainer restricts turbocharger lubrication. Replacement with a coarser-mesh strainer required. Without repair, turbo damage can result.
Symptoms: Power loss, whistling turbo noise, engine check light; in advanced cases metallic swarf in oil
At high mileages (150,000–200,000 km) 4.0 TFSI engines show timing chain stretch, recognisable by camshaft synchronisation faults. Repair requires extensive engine work on the V8.
Symptoms: Idle fluctuations, camshaft synchronisation fault codes, rattling on cold start from the front timing drive
The high-pressure fuel pump on the 4.0 TFSI is a known wear component. Pressure loss causes injection problems and uneven combustion. Wear increases with long service intervals or poor fuel quality.
Symptoms: Rough running, injection noise, power loss at high rpm, cold-start problems
Aluminium-silicon alloy cylinder walls are hard to repair once worn. Elevated oil consumption from piston ring wear occurs, especially with spirited driving and long intervals.
Symptoms: Steadily dropping oil level, slightly bluish smoke under acceleration, oil consumption above 1 litre per 1,000 km
A failed crankcase ventilation (PCV) routes engine oil into the intake channels. Unburnt oil entering the cylinders increases oil consumption and can cause knocking and power loss.
Symptoms: Blue smoke from exhaust, significantly elevated oil consumption, power loss, oily intake tract on inspection
The 4.0 TFSI cooling system relies on an electric main water pump (079121014M) and an auxiliary pump. Plastic housings and thermostat housing become porous with age. Failure creates overheating risk.
Symptoms: Coolant temperature rises unusually quickly or stays permanently low, coolant loss without visible leak, heater not working efficiently
The ZF8HP automatic transmission suffers from worn shift solenoids and torque converter when transmission fluid changes are missed. Shift jerk and overrun on gear changes are typical.
Symptoms: Jerk when pulling away or shifting, shift pauses in sport mode, in severe cases transmission limp mode, mechatronics fault codes
The hot-V architecture places turbos and spark plugs in the thermally extreme engine valley. Spark plug wear increases from around 40,000 km; CoD-deactivated cylinders (2, 3, 5, 8) are especially affected.
Symptoms: Misfires especially at CoD cylinders, stumbling at partial load, engine check light, misfire fault code
The vibration-damping engine mounts on the V8 suffer increased wear from torque impulses. According to used-car reports they typically need replacement from 50,000 km.
Symptoms: Vibrations in the passenger compartment under acceleration, audible movement when blipping and releasing the throttle, shift jerk at full load
The four lambda sensors (pre- and post-cat per bank) are exposed to extreme heat stress in the hot engine valley. Pre-cat sensors fail more often, causing rich mixture and elevated consumption.
Symptoms: Engine check light, increased fuel consumption, power loss, fault codes P0130–P0167 (mixture control)
Vehicle Weaknesses 4
An excessively fine oil strainer in the turbocharger oil feed causes oil starvation and can lead to turbocharger failure and engine seizure. Audi recalled all affected vehicles in 2022 (production June 2012 to March 2017, recall code 21H7).
Engine mounts on the S6 C7 frequently need replacing as early as 50,000 km. The 4.0 TFSI V8 is heavy and places severe stress on the mounts. A typical pointer when buying used.
The combination of 450 hp and two tonnes of vehicle weight leads to increased brake disc wear. The S6 C7's braking system is powerful but expensive to maintain.
The S6 C7 has many control units and a high quiescent current draw. Short trips prevent the battery from fully recharging, leading to control unit faults and starting problems.