Audi's flagship performance sedan combining a 520 PS twin-turbo V8 (605 PS in the S8 plus) with full luxury equipment and quattro all-wheel drive. The D4 generation delivers supercar-level power in an understated executive package, with adaptive air suspension, a ZF 8-speed automatic, and Cylinder on Demand technology. Depreciation has been steep, making it accessible at a fraction of its original list price.· more· less

Powerful yet refined twin-turbo V8 Enormous depreciation, strong value

Air suspension repairs are costly Turbo oil screen is a known weak point

Buy if: You want a fast, luxurious sedan and can budget for the occasional expensive repair that comes with this level of technology.

Avoid if: You need predictable, low running costs or cannot comfortably absorb a surprise bill in the €3,000-6,000 range.

Maintenance costs

€1,550 – €2,900/year

at 15,000 km/year

Fixed costsservice, tyres, brakes €950 – €1,700 /yr

Risk bufferunplanned repairs €600 – €1,200 /yr

Price estimates are based on German asking prices. Prices and costs vary by vehicle condition and location.

Maintenance costs

€1,550 – €2,900 per year

€950 – €1,700

service, tyres, brakes

€600 – €1,200

repair buffer

Buying a used Audi S8? Check its history.

carVertical scans 1,000+ databases for damage, mileage rollbacks, theft records and ownership changes. Save 20% with code CARCHECKER.

Affiliate link. Discount code CARCHECKER applied automatically.

Buying a used Audi S8? Check its history.

carVertical scans 1,000+ databases for damage, mileage rollbacks, theft records and ownership changes. Save 20% with code CARCHECKER.

Affiliate link. Discount code CARCHECKER applied automatically.

Common Problems

Turbo oil supply screen clogging

€3,000 - 12,0001 of 7

Oil strainer mesh in the engine valley clogs with carbon deposits, starving turbos of lubrication · more· less

The 4.0 TFSI has a small oil strainer screen in the engine valley that filters oil before it reaches the turbochargers. Over time, carbon deposits and debris accumulate in this screen, restricting oil flow to the turbo bearings. Once starved of oil, the turbo shaft develops play and can ultimately seize or disintegrate. Audi issued recall 21H7 for this, fitting a revised screen with larger perforations. The 2013-2017 model-year range usually quoted alongside it comes from the North American NHTSA campaign 22V178; in Europe the campaign applies per VIN and market, so have an Audi dealer check the individual car rather than assuming the build year decides it. Cars built after March 2017 already have the updated screen. However, even revised screens have been reported to clog on some pre-facelift cars. If caught early, a screen cleaning or relocation kit costs €750-1,500 at a specialist. If a turbo has already failed, replacement runs approximately €3,500-5,000 per turbo, and both turbos are commonly replaced together for €8,000-12,000 including labor. The hot-V configuration (turbos between the cylinder banks) makes access extremely labor-intensive.

Air suspension spring/strut leak

€1,200 - 6,0002 of 7

Rubber air springs deteriorate from age, UV, and road salt, causing one corner to sag overnight · more· less

The S8 D4 uses adaptive air suspension on all four corners. The rubber air spring bellows degrade over time from UV exposure, road salt, and general aging, developing small cracks that allow air to escape. The most common symptom is one corner of the car sitting noticeably lower after being parked overnight. This typically appears between 80,000-120,000 km, though some springs last longer. Aftermarket air struts (complete unit with damper and spring) from suppliers like Aerosus or Arnott cost €500-650 each, while OEM Audi struts run €1,200-1,800 per corner. The air compressor, which works harder to compensate for leaking springs, can also fail, adding €800-1,500 for replacement. A full suspension rebuild with four aftermarket struts plus a new compressor runs roughly €4,000-6,000, while an all-OEM job at an Audi dealer can exceed €10,000. At 100,000+ km, at least one strut replacement is very common.

Active engine mount failure

€1,500 - 3,0003 of 7

Electronically controlled hydraulic engine mounts leak fluid, causing heavy vibrations at idle · more· less

The D4 S8 uses active (electronically controlled) engine mounts that contain hydraulic fluid to dynamically dampen engine vibrations. When the mount housing cracks or seals deteriorate, the hydraulic fluid leaks out and the mount loses its damping ability. This manifests as heavy vibrations felt through the steering wheel and cabin, especially at idle in Drive with the brake applied. The vibration is typically most noticeable between 1,000-3,000 rpm. Each mount costs approximately €400-500 for the part, but the labor is substantial because of the limited access in the engine valley. A pair replacement runs €1,500-3,000 depending on whether it is done at a dealer or specialist. The left-side mount is particularly labor-intensive. Most mechanics recommend replacing both mounts together to avoid paying the high labor cost twice. Failure typically occurs between 80,000-120,000 km.

Carbon buildup on intake valves

€800 - 1,5004 of 7

Direct injection means no fuel wash on intake valves, allowing carbon deposits to accumulate gradually · more· less

Like all direct-injection engines, the 4.0 TFSI is susceptible to carbon buildup on the intake valves. Because fuel is injected directly into the combustion chamber rather than over the intake valves, there is no fuel wash to keep the valves clean. Over time, oily crankcase gases passing through the PCV system leave deposits on the valve backs, restricting airflow and causing rough idle, misfires, and reduced power. The only effective remedy is removal of the intake manifolds and physical cleaning of the valves, typically via walnut shell blasting. For a V8 engine this is more labor-intensive than a four-cylinder, with costs running €800-1,500 at a specialist. The issue is gradual and progressive, with some cars showing symptoms by 80,000 km while others remain acceptable past 150,000 km. Regular spirited driving helps slow the buildup compared to predominantly urban use.

Oil separator (PCV valve) failure

€300 - 6005 of 7

Crankcase vent valve fails causing a high-pitched whistle, rough idle, and lean fault codes · more· less

The PCV (positive crankcase ventilation) oil separator on the 4.0 TFSI can develop internal seal failures. When this happens, unmetered air enters the intake system, causing lean-running fault codes (commonly P0171 and P2187), rough idle, and often a distinctive high-pitched whistling noise from the engine bay. The failure is well documented on this engine and is a routine job for a specialist. The part itself costs approximately €150-250, and labor is typically €150-350 at a specialist, making this one of the more affordable repairs on the S8. Failure can occur at any mileage but is most commonly reported between 60,000-100,000 km.

Cylinder on Demand solenoid sticking

€800 - 2,0006 of 7

Cam lobe slider mechanism in the COD system can wear and stick, triggering limp mode · more· less

The 4.0 TFSI features a Cylinder on Demand (COD) system that deactivates four of the eight cylinders during light-load driving to improve fuel economy. Each cylinder has a switchable cam lobe on a spline on the camshaft. Over time, these sliding lobes can wear and become stuck, preventing proper cylinder reactivation. When this occurs, the engine runs roughly and enters limp mode. Many owners and tuners choose to permanently disable the COD system through an ECU remap, which eliminates the failure mode entirely. If mechanical repair is needed, individual solenoid replacement costs €800-2,000 depending on which cylinder is affected and how accessible it is. The issue is not extremely common but is more likely on cars that spend a lot of time in light-load motorway cruising where the COD system activates frequently.

Excessive oil consumption

€3,000 - 10,0007 of 7

Some engines use far more oil than others, and more than 0.5L per 1,000 km signals a real fault · more· less

Some 4.0 TFSI engines use noticeably more oil than others. Modest top-ups between services are normal on a high-output V8, but consumption above 0.5 liters per 1,000 km points to a fault rather than ordinary use. There is no Audi diagnosis or repair procedure published for the D4 S8 specifically, so treat this as an ownership risk to measure rather than a known factory fix. Ask for top-up records, look through the service history for repeated top-ups between intervals, and have a workshop run a measured consumption test if there is any doubt. If the cause turns out to be internal, the work means opening up a hot-V twin-turbo V8, which is extremely labor-intensive and runs €8,000-10,000+ at a specialist. A verified low-mileage used engine can sometimes be a more cost-effective solution at €3,000-5,000 plus installation. This is not a widespread failure across all 4.0 TFSI units, but it is worth checking consumption records before purchase.

Complex luxury sedan with known but manageable weak points

The 4.0 TFSI twin-turbo V8 is fundamentally robust, and many examples exceed 150,000 km without major powertrain failure. The main concerns are the turbo oil supply screen (addressed by recall), the adaptive air suspension (which wears on all cars at high mileage), and the active engine mounts. Most issues are well-documented and can be detected during a thorough pre-purchase inspection. Cars with a complete Audi service history and documented recall completion are significantly lower risk. Budget for air suspension work as a near-certainty at high mileage.

Pre-Purchase Inspection Checklist

Viewing checklist for the Audi S8 4.0 TFSI D4

A printable one-page A4 checklist for this model.

General checks

Service history
Complete Audi dealer or specialist records essential. The 4.0 TFSI requires 8.5 litres of oil and has strict service intervals.
Tires
Check tread depth, age (date codes), and uneven wear. 20/21-inch tires are expensive to replace.
Cold start
Must start the engine completely cold. Listen for any rattling, turbo whine, or unusual sounds in the first 30 seconds.
Test drive
Minimum 30 minutes including highway speeds. The ZF 8-speed should shift smoothly in all modes.

Specific for this vehicle

Verify turbo oil screen recall (21H7) completed
This is the single most important check. Ask for documentation that Audi recall 21H7 has been performed, and have an Audi dealer confirm by VIN whether it applies to this car, because applicability varies by market and build date. If it applies and is outstanding, budget for the screen service immediately.
Check for air suspension sag overnight
If possible, park the car on level ground overnight and check whether all four corners remain at equal height the next morning. Any sag indicates a leaking air spring.
Test all suspension ride height modes
Cycle through lift, comfort, auto, and dynamic modes. Each should respond within a few seconds. Slow or unresponsive leveling indicates compressor or valve block issues.

+ 4 more checksShow less

Check for engine mount vibration at idle
With the engine warm, hold the car stationary in Drive with the brake pedal pressed. Heavy vibration through the steering wheel or cabin indicates failed active engine mounts.
Check the oil level after the test drive, the way the manual specifies
Read the level once the engine is at operating temperature, with the car standing level, the engine switched off, and roughly two minutes' waiting time. Cars with the oil-level indicator show it in the MMI; the dipstick procedure needs the same warm engine and the same wait. Ask the seller about oil consumption history and top-up frequency.
Listen for PCV whistle at idle
With the engine idling and the hood open, listen for a high-pitched whistling noise from the engine bay. This indicates a failing oil separator.
Inspect under the car for oil leaks
Look for oil seepage around the engine valley (between the cylinder banks), turbo oil lines, and engine mounts. The hot-V layout makes leaks hard to spot from above.

Recalls and Technical Service Bulletins

Turbo oil supply screen clogging, 4.0 TFSI (Audi 21H7; the 2013-2017 range comes from North American NHTSA campaign 22V178, European applicability is VIN and market specific) Critical - verify completed

Engine-compartment seal can loosen and touch hot components, creating a fire risk; remedy is a retaining plate (Audi 51G6 / EU A12/01262/20, 4.0 TFSI S8 and S8 plus type 4H) Critical - verify completed

Takata airbag inflator (check VIN applicability) Verify with VIN

The turbo oil screen recall is the most critical item. Contact an Audi dealer with the VIN to check whether recall 21H7 applies to this car and has been completed; the widely quoted 2013-2017 range is from the North American campaign, so European applicability is decided by VIN and market rather than by build year. Have the same VIN check cover campaign 51G6 (EU reference A12/01262/20), the engine-compartment seal fire risk on the 4.0 TFSI S8 and S8 plus type 4H, which Audi workshops throughout the EU can carry out. Also verify whether any Takata airbag recalls apply to your specific car, as coverage varies by production date and market.

Warranty Status

Factory warranty (2 years) Expired on all D4 S8s

Rust perforation warranty (12 years) May still be active on 2014+ cars

All D4 S8s are outside their original 2-year factory warranty. Extended warranty options through Audi dealers are available but become increasingly limited and expensive as the cars age. The rust perforation warranty may still cover body panels on later production cars.

↔ Also consider

Bentley Flying Spur 4.0 V8 Mk2 2014-2019

Same 4.0 TFSI engine with similar turbo oil screen and air suspension issues. Higher purchase price and parts costs, but identical core risks.

Mercedes-Benz S500 W222 2013-2017

BMW M5 F10 2011-2016

More performance-focused with rod bearing and VANOS concerns. Higher running costs and harder on consumables, but no air suspension.

BMW 740i F01 2008-2015

Simpler inline-6 turbo engine avoids the V8 complexity. Lower risk profile but also significantly less power.

Lexus LS 460 XF40 2006-2017

Far more reliable V8 with much lower running costs. Air suspension is the only shared weak point. Slower and less engaging to drive.

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.