Audi S6/S7 4.0T Problems: The 420hp Sedan/Sportback Reliability Guide
Common Failure Points & Costs
| Component | Failure Mileage | Symptom | Est. Cost (USD) | Risk Level |
|---|---|---|---|---|
| Turbo Oil Screen (Oil Module) | 40k - 80k miles | Screeching noise, loss of power, check engine light | $700 - $1,700 (Preventive) / $5,000 - $8,000 (Turbo Replacement) | Critical |
| PCV / Oil Separator (Valley) | 60k - 100k miles | Whistling noise, strong vacuum at oil cap, idle instability | $1,000 - $2,000 | High |
| S-Tronic DSG (Mechatronic) | 70k - 100k miles | Harsh shifts, delayed engagement, limp mode | $2,500 - $4,000 | High |
| Carbon Buildup (Intake Valves) | 50k - 70k miles | Rough idle, hesitation, misfires | $800 - $1,200 | Medium |
| Coolant Thermostat | 60k - 90k miles | Overheating, coolant leak | $600 - $1,000 | Medium |
| Rear Differential Bushings | 60k - 90k miles | Clunking on acceleration, vibration | $500 - $1,000 | Medium |
Reliability Verdict
The S6/S7 C7 are 420hp performance sedans with the same turbo oil screen flaw as all 4.0T engines. If the recall (TSB 2044640) has been completed, they're fantastic daily drivers. If not, you're gambling with a $8,000 turbo replacement. The S-Tronic DSG is generally reliable but can develop mechatronic issues.
Audi S6/S7 4.0T Problems: The $16,000 Used Performance Sedan Gamble
The Audi S6 and S7 C7 are 420hp performance sedans that can hit 60mph in 4.4 seconds while returning 25mpg on the highway. They’re the cars that make BMW 550i buyers jealous.
But on the used market, they’re financial traps. You can buy a $90,000 S7 for $20,000. Why? Because the turbo oil screen clogs, the PCV fails, and the DSG mechatronic unit can fail.
This guide breaks down exactly what fails on the S6/S7 C7, distinguishing between the early C7 (2013-2015) and the improved C7.5 (2016-2018).
1. The S6/S7 C7 vs C7.5: Two Different Animals
You must understand the difference between the pre-facelift and facelift models.
S6/S7 C7 (2013-2015)
- Engine: EA824 4.0T V8 (420hp)
- Risk Level: HIGH
- Why: Early oil screen design, higher turbo failure incidence, early DSG software.
- Recall Coverage: 2013-2017 S6/S7 is covered by TSB 2044640.
- Verdict: Buyable, but only with recall completion verified.
S6/S7 C7.5 (2016-2018)
- Engine: Updated EA824 4.0T V8 (450hp)
- Risk Level: MODERATE
- Why: Revised oiling system, updated DSG software, better build quality.
- Verdict: The smart buy. Still has carbon buildup and PCV risk, but lower turbo failure rate.
2. Common Failures & Costs
A. Turbo Oil Screen (The Existential Risk)
The S6/S7 shares the same turbo oil screen flaw as all 4.0T engines. See our Audi 4.0T V8 Pillar Page for the full technical breakdown.
- Symptom: Screeching noise, loss of power, check engine light.
- Test: Listen for a high-pitched screech on acceleration. If present, walk away.
- Cost: $5,000 - $8,000 for turbo replacement.
[!WARNING] Critical: If the oil screen recall (TSB 2044640) has not been completed, the car is a ticking time bomb. Verify recall completion before purchase.
B. S-Tronic DSG (Mechatronic)
The S6/S7 uses the S-Tronic dual-clutch transmission (DSG). The mechatronic unit can fail.
- Symptom: Harsh shifts, delayed engagement, limp mode, “Transmission Fault” warning.
- Mileage: 70,000 - 100,000 miles.
- Fix: Mechatronic unit replacement.
- Cost: $2,500 - $4,000.
[!TIP] Preventive Maintenance: Change DSG fluid every 40,000 miles (Audi says “lifetime” but this is inadequate). Use VW G 052 182 A2 fluid only.
C. PCV / Oil Separator Failure
The PCV system in the valley fails, causing whistling noises and idle instability.
- Symptom: Whistling noise from the engine bay, strong vacuum at oil cap, idle fluctuation.
- Test: Remove the oil cap while idling. If the idle changes dramatically or you hear loud hissing, the PCV is failing.
- Cost: $1,000 - $2,000.
3. Maintenance Budget
Owning an S6/S7 C7 is not like owning an A6/A7. It is a performance-level maintenance schedule.
- Oil Changes: Every 5,000 miles (Mandatory). Audi’s 10,000-mile interval will clog the oil screen.
- Tires: Rear tires last 15,000-20,000 miles. Expect $1,400/set.
- Brakes: Large rotors. Expect $1,500/axle.
Annual Expectation: $3,500 - $5,000 in non-routine repairs.
4. The “Bargain” Trap
Scenario: You see a 2014 Audi S7 with 68k miles for $20,000. It looks clean.
Reality: It likely needs:
- Oil screen recall verification (if not done: $8,000)
- PCV replacement ($1,500)
- Carbon cleaning ($1,000)
- DSG mechatronic ($3,000)
Total Immediate Cost: $5,500 (or $13,500 if turbo oil screen has not been addressed).
You have effectively doubled the price of the car in the first month.
5. Should You Buy One?
YES, IF:
- You are looking at a 2016+ C7.5 model.
- You can afford a $4,000/year maintenance budget.
- You have a trusted Audi specialist nearby.
- You get oil screen recall verification and clean PCV inspection.
NO, IF:
- You are stretching your budget to buy the car.
- You rely on the dealer for service.
- You need 100% reliable transportation.
- You cannot afford a potential $8,000 turbo replacement or $4,000 transmission repair.
6. The Safer Alternative: The A6/A7 3.0T
Unless you need 420hp, buy the A6/A7 3.0T (supercharged V6).
- Engine: 3.0T V6 (333hp)
- Reliability: Significantly better. No turbo oil screen. No PCV valley failures.
- Power: 333hp (Still very fast).
- Risk: Lower. Proven engine.
7. Verdict
The Audi S6/S7 C7 is a performance bargain if you know what you’re doing. It offers 420hp, a glorious exhaust note, and the prestige of the Audi brand for the price of a used Camry.
But it requires a “performance” budget to keep running. If you go in with open eyes and a full wallet, it’s a rewarding experience. If you treat it like a Toyota, it will bankrupt you.
Related Guides:
Expert Buying Advice
Only buy an S6/S7 C7 with: 1) Documented oil screen recall completion (TSB 2044640), 2) Clean PCV (no whistling), 3) Transmission shifts smoothly. Avoid 2013-2014 models without recall. The 2016+ C7.5 S6/S7 is the smart buy. Budget $3,500/year for maintenance.