Audi S6 C7

4.0 TFSI V8 twin-turbo with 309 kW — turbos sit between cylinder banks (hot-V layout), extreme heat stress. Recall 21H7 (April 2022, 76,098 vehicles): oil screen in turbo supply too fine-meshed, clogs from oil/carbon deposits → turbo bearing wears → turbine shaft breaks. Fix: coarser screen. Turbos wear from 60,000–80,000 km, repair in five-figure range. V8 timing chain stretches from 150,000–200,000 km. Increased oil consumption from 60,000 km due to direct injection and aluminium-silicon bore surfaces. Camshafts factory-paired to respective head — damage means pair replacement only, extremely expensive. 10 documented weaknesses. Oil every 10,000 km with 5W-30, never longlife. When buying used: check recall 21H7 first.

• !! Recall 21H7 — Oil Strainer Turbocharger Supply from 60,000 km

  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
  0–500 $
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• !! Timing Chain Stretch — V8 BiTurbo from 170,000 km

  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
  3,000–8,000 $
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• !! High-Pressure Fuel Pump — Wear from 140,000 km

  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
  800–2,500 $
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+ 7 more engine weaknesses + vehicle weaknesses

4.0 TFSI V8 twin-turbo with 331 kW — S6 Performance, same base as CTGA with higher mapping. All CTGA weaknesses apply: recall 21H7 (turbo oil screen), turbo wear from 60,000 km, timing chain, oil consumption, camshafts pair-only. Additionally: S-Tronic 7-speed DCT as weakness — judder/shudder on launch, "gearbox overheated" warning with spirited driving. Mechatronic defects at higher mileages. Gearbox oil change every 60,000 km essential (despite Audi "lifetime fill"). Revision €3,000–5,000. Turbos under more stress from performance mapping than standard S6. Oil every 10,000 km, no longlife.

• !! Turbocharger Damage from Insufficient Lubrication from 70,000 km

  Turbocharger damage occurs frequently on the 4.0 TFSI V8 and is attributed to insufficient oil supply. First signs often appear from 60,000–80,000 km with power loss and noise.

  Symptoms: Power loss, whistling or howling noises, elevated oil consumption, blue smoke
  3,000–8,000 $
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• !! Cylinder Bore Coating Damage from 150,000 km

  The aluminium block with coated cylinder bores does not allow conventional oversize piston repair. Damage requires expensive engine replacement or complete overhaul.

  Symptoms: High oil consumption, power loss, blue smoke, combustion noise
  8,000–20,000 $
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• !! S-Tronic DCT as the Weak Point from 100,000 km

  The S-Tronic dual-clutch gearbox is the weakest link in the S6 C7 drivetrain. Aggressive driving and power fluctuations at higher rpm put additional strain on the DCT.

  Symptoms: Jerk on gear changes, clutch slip, overheating warning, failed shifts
  3,000–8,000 $
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+ 2 more engine weaknesses + vehicle weaknesses