Premium German executive sedan offering strong performance and advanced technology. The EA839 3.0 TFSI engine itself is considered robust with high-mileage examples existing, but the 48V mild hybrid system (Belt Starter Generator and DC-DC converter) has proven problematic across 2018-2020 models - verify replacement before purchase. Other concerns include MMI infotainment freezes, DL382 transmission jerkiness at low speeds, and carbon buildup on intake valves. Early 2019-2020 models may have reliability teething problems. Improved significantly in 2023 What Car? survey (90.2%) after finishing last in class in 2021 (76.3%).
Expected Annual Maintenance Costs
€1,100 - €2,100/year
15,000 km/year
Fixed costs
€650-1,000
Risk buffer
€450-1,100
What Can Break
bars = likelihood
48V Belt Starter Generator (BSG) failure€1,500 - €3,500
Known factory defect causing complete electrical system shutdown · more· less
The Belt Starter Generator is a major known issue affecting 10-15% of 2018-2020 A6/A7/A8/Q7/Q8 models with the 48V mild hybrid system. Symptoms progress from auto start/stop malfunction to complete electrical failure - loss of steering, brakes, transmission, and engine within 20 minutes. Many owners report being stranded. Audi issued recall campaign 27H2 for moisture ingress in 2.0 TFSI models, but 3.0 TFSI models also affected. A 2024 class action settlement extended warranty to 10 years for BSG failures. Replacement costs €1,500-1,800 at dealer. When buying used, verify BSG has been replaced with updated part number - this is the single most important check for this generation.
DC-DC converter (48V to 12V) failure€2,000 - €5,300
Voltage converter fails, causing "Electrical System Malfunction" warning · more· less
The DC-DC converter steps down 48V to 12V to charge the conventional battery. When it fails, the 12V battery rapidly discharges, showing warning lights and battery icons on the instrument panel. The car may enter limp mode or shut down completely. Out-of-warranty replacement costs approximately €2,000-5,300 including the 48V battery (€4,000 alone). Often occurs alongside BSG failure. Some cases show evidence of coolant intrusion. This is related to the overall 48V system reliability issues plaguing early C8 models.
MMI infotainment system freeze/glitches€0 - €800
Touchscreen freezes, slow boot times, Bluetooth disconnects, navigation errors · more· less
The MMI system is reported to have numerous bugs. Common issues include taking up to 1 minute to boot when starting the car with no access to features during boot, steering wheel volume/mute buttons occasionally not functioning (requires restart), Bluetooth disconnecting during calls, and Spotify/media freezing while audio continues playing. After software updates, some owners report new problems including iPhone disconnection requiring re-registration and navigation getting stuck on loading indicators. Quick fix: press and hold volume knob for 10 seconds to reset. Persistent issues may require dealer software update (usually free if under warranty) or in rare cases, MMI control unit replacement (€800+). What Car? survey noted 44% of C8 A6s had faults, with two-thirds concerning electrical systems or infotainment.
Rough shifting at low speeds, hesitation between gears, clunky operation · more· less
The 7-speed DL382 dual-clutch transmission (updated from DL382+/0HL with 500 Nm torque capacity) is reported to be uncomfortable in city driving with jerky shifts, particularly between 1st and 2nd gear in heavy traffic. The transmission upshifts very quickly to higher gears in Comfort mode, exaggerating roughness. Using Dynamic/Sport mode helps but holds gears too long. Some owners report hesitation when accelerating and harsh gear engagement. Software updates can improve behavior (€500-800). More serious issues like mechatronics failure, gear not engaging, or clutch shuddering can cost €1,500-3,500. Regular transmission fluid changes help prevent problems. The transmission is considered adequate for normal driving but not as refined as competitors' torque converter automatics.
Carbon buildup on intake valves€800 - €1,800
Direct injection causes carbon deposits, needs walnut blasting around 80,000 km · more· less
All direct-injection engines suffer from intake valve carbon buildup because fuel doesn't wash over the valves. Symptoms include rough idle, hesitation, reduced power, and increased fuel consumption. Typical interval for cleaning is 60,000-100,000 km. The only effective solution is removing the intake manifold and physically cleaning valves via walnut shell blasting. Dealer costs range €1,200-1,800, independent specialists charge €800-1,200. Some preventive measures help: using premium fuel, occasional spirited driving to higher RPMs, and catch can installation. Fuel additives do NOT work for intake valve carbon on direct-injected engines. Budget for this service every 80,000 km.
Water pump / thermostat housing failure€650 - €1,600
Plastic thermostat housing cracks, water pump leaks around 70,000-100,000 km · more· less
The 3.0 TFSI uses a plastic thermostat housing that can crack from temperature cycling, with tabs that hold the thermostat breaking over time. Early thermostats could stick closed causing overheating. Symptoms include coolant warning light, loud fan noise, AC stops working, and engine temperature rising. One owner discovered coolant leaks around the coolant shutoff valve at 65,000 miles requiring water pump, thermostat, coolant shutoff valve, and water pump vacuum solenoid replacement for $2,600 (€2,400). Dealer replacement costs €750-1,000 for thermostat, €1,100-1,600 for water pump. Independent shops charge €650-1,200. Some owners upgrade to aluminum housing to prevent future failures. If thermostat has failed and caused overheating, replace water pump too.
Turbocharger actuator sticking€500 - €2,500
Carbon buildup from gentle driving causes EPC light and limp mode · more· less
The turbo wastegate actuator can stick if the car is driven too gently or only for short trips, as carbon deposits accumulate. Symptoms include EPC (Electronic Power Control) warning light, sudden loss of power, and limp mode. Audi dealers typically won't sell the actuator separately, requiring full turbo replacement at €1,800-2,500. Specialist shops can replace just the actuator for €500-700. If turbo internals are damaged from prolonged actuator issues, full replacement is necessary. Prevention: use premium fuel, occasional spirited driving to higher RPMs, and ensure proper warm-up/cool-down cycles. Avoid only short trips if possible.
Oil leaks (oil pan gasket, valve covers)€200 - €800
Gaskets deteriorate over time causing oil seepage, typically after 100,000 km · more· less
Forum data shows approximately 8% of C8 55 TFSI quattro owners report oil leaks, most commonly from the oil pan gasket. As rubber gaskets age, they become brittle and leak. Symptoms include oil spots under the car after parking and oil smell in the cabin. Oil pan gasket replacement costs €300-400 at independent shops, €500-600 at dealers. Valve cover gaskets can also leak, costing €400-800 to replace. While not an immediate safety issue, oil leaks should be addressed promptly to avoid damage to other components and environmental issues. Regular inspection during oil changes helps catch these early.
Decent reliability for luxury sedan, but avoid early 48V MHEV models
The EA839 3.0 TFSI engine is fundamentally reliable with examples exceeding 250,000 km when maintained properly. However, the 48V mild hybrid system (BSG and DC-DC converter) has proven to be a significant weak point in 2018-2020 models, with Audi issuing recalls and a class action settlement. The MMI infotainment and transmission refinement issues are frustrating but rarely catastrophic. For a used purchase, verifying BSG replacement is critical. Overall reliability improved significantly in later production years as Audi addressed early teething problems.
Pre-Purchase Inspection Checklist
General checks
Service history Complete Audi dealer or authorized specialist records essential. Verify oil changes every 15,000 km or annually.
Tires Common sizes 245/45R19 or 255/40R20. Check tread depth (minimum 3mm), age (max 6 years), and uneven wear patterns.
Cold start Must start engine completely cold. Listen for unusual noises, rattles, or rough idle.
Test drive Minimum 30 minutes including city traffic and highway speeds. Test all driver assistance features.
Body condition Check for accident damage, paint mismatch, and proper panel gaps. Aluminum body means expensive repairs.
Specific for this vehicle
CRITICAL: Verify 48V BSG replacement Ask dealer/seller if Belt Starter Generator has been replaced with updated part. Check service records. This is THE most important check for C8 A6. Contact Audi with VIN to verify recall/warranty extension status.
Test MMI infotainment thoroughly Test touchscreen responsiveness, navigation, Bluetooth pairing/calls, media playback. Check boot time when starting car. Press and hold volume knob 10 seconds to test reset function.
Evaluate transmission behavior Drive in stop-and-go traffic for 15+ minutes. Feel for jerky 1-2 shifts, hesitation, or clunking. Test both Comfort and Dynamic modes. Transmission should be smooth when fully warm.
Check for electrical warning lights On test drive, watch for any "Electrical System Malfunction" warnings, battery icons, or multiple systems failing simultaneously. These indicate 48V system issues.
Inspect coolant system Check coolant level, condition (should be pink/red, not brown), and look for leaks around water pump, thermostat housing, and hoses. White residue indicates past leaks.
Listen for turbo actuator issues Accelerate briskly - should be smooth power delivery. EPC light or sudden power loss indicates actuator problems. Check for wastegate rattle on deceleration.
Check for carbon buildup symptoms Rough idle, hesitation, or lack of power especially when cold may indicate carbon buildup on intake valves. Ask when/if carbon cleaning was last performed.
Verify all driver assistance systems work Test adaptive cruise control, lane keep assist, parking sensors, 360 camera, traffic sign recognition. Many rely on the electrical system.
Air suspension check (if equipped) Test all ride height settings (lift, auto, comfort, dynamic). Listen for compressor noise. Car should not sag overnight when parked.
Front side airbag crash sensor fault (July-Sept 2020 production)Verify completed
Belt Starter Generator extended warranty (Class Action Settlement 2024)10 year coverage - Check status
MMI software updates for infotainment glitchesCheck if latest applied
Contact Audi dealer with VIN to verify all recalls completed. The 48V BSG recall (27H2) and class action settlement warranty extension are particularly important. Check NHTSA database for additional TSBs. According to the 2024 class action settlement, Audi extended the BSG warranty to 10 years from in-service date - verify your vehicle is covered.
Warranty Status
Factory warranty (New Vehicle Limited)4 years / 80,000 km
Corrosion warranty12 years / unlimited km
48V BSG extended warranty (post-settlement)10 years / 160,000 km
Audi Pure Protection extended warranty€3,200-4,700/year (optional)
Most 2018-2020 C8 A6s are now outside the original 4-year factory warranty. However, the 2024 class action settlement extended BSG coverage to 10 years from in-service date. Audi Pure Protection extended warranties available in three tiers (Powertrain, Gold, Platinum) with €0-250 deductible options. Cost increases significantly after 16,000 km. Given the BSG issues, extended warranty may provide peace of mind, though BSG itself is now covered for 10 years.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.