Audi S6 Avant
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 9
On model years 2015–2018, the locking bolt of the tow bar can fracture, potentially causing the trailer to become detached while driving. Free workshop visit required.
The Multitronic CVT gearbox has a notoriously poor reliability record. Improved on the C7, it remains a risk. Total failure possible from 100,000 km; repair is very costly.
A material defect can cause the camshafts in the 3.0 TDI to fracture, leading to engine damage. Mainly affects vehicles from model year 2014 to early 2017.
The optional air suspension (AAS) is prone to failure through porous air bellows and defective compressors. Repair costs of 600–1,800 EUR per corner are possible.
LED headlights fail due to defective control modules or individual LEDs. Repair is often more expensive than replacement, as modules cannot be replaced individually.
The automatic climate control shows malfunctions from around 60,000 km: incorrect temperature regulation, blower stage issues or complete failure of individual zones on the three-zone system.
Wheel bearings, particularly at the rear axle, show increased wear at higher mileages. Regularly flagged on vehicles from 80,000 km.
On the C7, rust occurs primarily on the underbody and sills, sometimes in hard-to-reach areas. On vehicles over 7 years old, the underbody should be thoroughly inspected.
On V6 and V8 engines, engine mounts often wear from around 50,000 km, causing noticeable vibrations.
Reports & Tests
262 owner complaints filed with NHTSA (2011–2018). Most reported: Airbags (69), Engine (59), Electrical (37).