Audi S8
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.
520 hp sleeper — retiree sedan, supercar thrust
Twin-turbo V8 in stealth mode — looks like a retiree's sedan, hits like a freight train at full throttle. Better power-to-weight than a 911 Carrera 4S. Cold start loud enough to set off car alarms. A bargain used, as long as air suspension and turbo lines hold up.
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 13
The adaptive air suspension on the A8 D4 is a well-known money pit. Air bellows become porous, the compressor runs non-stop and overheats. Repairing all four corners costs several thousand euros.
The 4.2 TDI V8 in the A8 D4 has a timing chain that is prone to premature wear when neglected. A break causes severe engine damage. Replacement requires complete engine removal.
The 4.2 FSI V8 has four timing chains with phenolic resin guide rails that become brittle with age. Neglected oil changes risk chain skip.
Turbocharger bearings can wear and bring the turbine wheel into contact with the housing. Audi recalled around 26,000 vehicles in 2022.
Leaking air bellows cause the vehicle to sink and force the compressor into continuous operation until it fails. Front and rear are equally likely to be affected.
The MMI multimedia system stands out from 60,000–100,000 km with frozen screens and unresponsive controls. Multiple control modules can be affected.
The ZF 8-speed automatic shows harsh gear changes and gear selection problems at high mileage. Regular oil changes (every 80,000 km) are critical.
The MMI multimedia system is known for total failures caused by overvoltage damage after battery replacement or moisture damage to the Bluetooth control module.
The rubber-metal bushes of the front control arms on the heavy A8 D3 show significant wear at high mileage.
Front and rear control arm rubber bushes go soft with increasing mileage. The A8's considerable weight accelerates wear.
The 6-speed Tiptronic shows harsh gear changes at high mileage. A gearbox oil change often resolves the problem.
With increasing age the driver's side window regulator switch block on the A8 D3 frequently fails. The switch block must be completely removed for replacement. Pixel failures in the instrument cluster and screen faults are further typical age-related symptoms.
Almost all A8 D3s show worn and peeling soft-touch surfaces on light switches, trim panels and control knobs. The coating detaches in strips, leaving a sticky surface that is visually badly affected.
Reports & Tests
124 owner complaints filed with NHTSA (2010–2017). Most reported: Engine (78), Other (13), Fuel System (12).