Audi S8
Biturbo V8 with 420 kW and 48V mild hybrid in the S8 D5. Flagship engine with cylinder deactivation and enormous power delivery. Luxury and performance combined.
571 hp luxury sedan — perfectly insulated, almost too perfect
Twin-turbo V8 with 48V, predictive suspension that reads the road ahead. Absurdly fast yet so quiet that speed feels unreal. Autocar: 'V8 lends bucketfuls of soul'. But that very isolation is the problem — the 571 hp are barely felt. A technical masterpiece that forgets to be an experience.
Engine Weaknesses 9
The oil strainer inside the engine clogs and cuts off the turbocharger lubricating oil supply. Vehicles fail without warning. In the US, 58 official complaints were registered.
Symptoms: Sudden engine shutdown without warning, power reduction, turbo noises
The high boost pressures of the BiTurbo configuration heavily stress charge air hoses and seals. Leaks cause power loss up to limp mode.
Symptoms: Power dip, engine stumbling under load, noticeable limp mode, whistling noises from the engine bay
Hitachi high-pressure pumps wear on the tappet rods. Improved tappet rods were introduced as a replacement part. A pump failure manifests as starting problems and rough running.
Symptoms: Difficult starting, rough engine running, power loss especially at higher rpm
Worn or contaminated turbochargers produce noticeable turbo lag and reduced peak power. The BiTurbo configuration increases failure risk through two units.
Symptoms: Noticeable hesitation when accelerating, muted peak power, whistling from the turbo
The S8 D5 DHRA shares the PCV issue of all 4.0 TFSI V8 derivatives. Defective oil separator membrane causes uncontrolled oil entry into the intake; if unaddressed, damage to intake valves and turbochargers follows.
Symptoms: Blue smoke, increased oil consumption, oil film inside the air filter housing, sooty spark plugs
The RSG (part number 4N0→4N1 revised) is known to be problematic in the S8 D5 as well. Multiple failures within short periods documented; KBA recall 2020 for moisture ingress.
Symptoms: Electrical system warning, vehicle will not start, 48V system fault, mild hybrid shutdown, in extreme cases: vehicle stops while driving
The elaborate thermal management system of the S8 D5 with electric main water pump (079121014M) and auxiliary pump is prone to failure. Failure of the electric pump after shutdown risks heat soak in the turbo system.
Symptoms: Coolant temperature continues to rise briefly after shutdown, heater failure, low coolant warning, overheating indicator
Above 2,500 rpm, piston cooling jets spray oil under the pistons. With spirited driving, some of this burns off, creating regular top-up requirements between service intervals.
Symptoms: Dropping oil level between oil changes, bluish smoke from the exhaust during throttle bursts
The S8 V8 also uses CoD; the thermally stressed spark plugs of the deactivated cylinders should be replaced every 40,000 km. Hot-V position makes replacement labour-intensive and expensive.
Symptoms: Rough running on cold start, misfire warning indicator, light stumbling under partial load, especially after CoD reactivation
Vehicle Weaknesses 4
The S8 D5's suspension comes as standard with Adaptive Air Suspension. Air bellows and compressor wear over the years. Repair costs are substantial and very high at luxury-vehicle workshop rates.
Like all 48V mild-hybrids on the platform, the S8 D5 is affected by the BSG problem. When the component fails the entire 48V system goes offline. Audi grants a 7-year extended warranty on the part.
The S8 D5 is optionally available with carbon-ceramic brakes. These are powerful but extremely expensive to replace. The cost of a full replacement set runs into four figures.
The S8 D5 has one of the most complex electronic architectures of any car. Sporadic faults in assistance systems, infotainment and suspension control are reported. Software updates fix many problems.
Reports & Tests
1 owner complaints filed with NHTSA (2019–2024). Most reported: Powertrain (1), Electrical (1), Engine (1).