The Audi S4 B8 combines a supercharged 3.0-litre petrol V6, quattro traction and discreet saloon or Avant bodywork. It can be a practical everyday performance car, but an inexpensive example still contains an expensive engine installation, transmission and chassis. Buying well means checking cooling-system history, crankcase ventilation, gearbox behaviour and the actual specification beneath a familiar Audi badge.
Our buying verdict
Choose a documented standard or coherently modified car with a healthy cooling system, complete gearbox evidence and an independent VAG inspection. A facelift is worth considering, but it is not a guarantee against repair bills. A working optional sport differential is attractive; neglected tyres, unexplained coolant loss or hot gearbox faults should carry much more weight than a long equipment list.
Understand the B8 and B8.5 S4
This guide covers the supercharged petrol V6 generation and its facelift, commonly called B8.5. It does not cover the earlier V8 S4 or the later B9 engines. The TFSI badge should not lead you to describe this B8 engine as turbocharged: its forced induction comes from a mechanically driven supercharger.
| Choice | Why consider it? | What to establish |
|---|---|---|
| Early B8 | Discreet styling and potentially attractive purchase cost. | Cooling repairs, gearbox history, actual engine and transmission codes. |
| Facelift B8.5 | Updated styling, equipment and mechanical revisions. | Exact build and component history; a later registration does not make every assembly immune to faults. |
| Saloon | Traditional performance-saloon shape. | Boot condition, water ingress, rear body repairs and equipment. |
| Avant | More flexible load space for everyday use. | Tailgate, load area, rear wiring, seals and any evidence of towing use. |
| Six-speed manual | Conventional shift experience where fitted. | Clutch, flywheel, leaks and genuine specification. |
| Seven-speed S tronic | Dual-clutch convenience and fast shifts. | DL501/0B5 service evidence, diagnostic assessment and full hot-and-cold test. |
Verify factory options with the build specification. Drive select menus, badges and seller descriptions do not alone prove a sport differential or adaptive damper installation. If the car has those systems, test and scan them, then inspect the associated hardware and leaks.
Market specifications and model-year labels differ, especially when using US service material. Confirm the individual engine and transmission codes before ordering parts or adopting an interval. A UK car’s registration year and an American guide’s model year are not necessarily equivalent.
Decide what you need before shopping. An Avant with good maintenance can be a better family purchase than a cheaper saloon that fails your space requirements. Equally, a large-wheel, lowered, loud example may be much less pleasant on your daily route than a standard car.
Prices and buying priorities
A limited UK check on 4 November 2026 found a 2013 S4 Avant Black Edition S tronic advertised on PistonHeads at £12,990 with 80,000 miles. This is one asking-price observation and an unverified seller description, not a representative market range or an achieved sale price.
Compare several cars with the same body, generation and gearbox before making an offer. Do not blend later diesel or turbocharged S4 prices into a supercharged B8 valuation. Check whether advertised options are genuine and whether recent major maintenance is documented.
Work from total first-year cost. An attractive asking price can be overwhelmed by cooling work, transmission diagnosis, tyres and suspension repairs. Obtain independent estimates for identified defects, and keep money available after the purchase. A seller’s claim that a warning “just needs a service” is not a diagnosis.
Bodywork, underside and water checks
Inspect the car dry in daylight and on a lift. Compare panel gaps, paint finish and fixings, then examine structural areas behind previous repairs. Check bumpers, undertrays, the cooling pack and wheelarch liners for impact damage or poor refitting. A clear history report does not prove every accident was recorded.
Look at sill and jacking areas, subframes, suspension mountings, brake pipes and exhaust fixings. Ask for evidence behind any recent underside coating. Lift inspections can reveal damaged shields and leaks that disappear from view when the car is parked normally.
Check beneath carpets and the luggage floor for dampness. Test a sunroof or panoramic roof if fitted and inspect seals and drains with appropriate care. Water can affect wiring and control units, so a drying-out explanation should include the cause and any resulting repairs.
Examine wheels for cracks, bends and poor refurbishment. Tyre wear should agree with the alignment and suspension story. Incorrect or poorly matched tyres deserve particular attention on a four-wheel-drive performance car: establish suitable sizes, ratings and compatibility with a specialist.
Supercharged V6 checks
Cold start, oil history and fault diagnosis
Arrange a genuinely cold start. Check oil and coolant using the proper safe procedures, listen for persistent abnormal mechanical noise and watch for smoke, rough running or warnings. A briefly demonstrated warm engine tells you less about start-up behaviour. Ask about oil use between services and retain a chronology of invoices.
Read engine and transmission codes with appropriate VAG equipment. A warning-free dashboard is not a complete health report, particularly if faults were recently cleared. Ask the inspector to interpret current and stored faults alongside live operation, rather than selling you a list of speculative replacement parts.
The camshaft drive uses chains, while the supercharger and accessories have belt drives. Do not buy a generic timing-belt kit as routine camshaft maintenance. Persistent start-up noise, timing-related faults or oil-pressure concerns need a proper assessment; a chain-driven engine is not automatically free of expensive timing work.
Water pump, thermostat and hidden coolant leaks
FCP Euro’s original B8/B8.5 repair procedure documents water-pump and thermostat access, including supercharger removal and placing the front end into a service position for its demonstrated method. This is why a cheap component price does not describe a complete repair. Confirm the exact procedure and scope with the garage working on your engine.
Look for coolant residue, a sweet coolant smell, low level, repeated topping-up and unstable temperature behaviour. Check warm-up, fans and stored thermostat-related faults. A thermostat problem and a leaking pump are different diagnoses, even when it is sensible to discuss related work during the same visit.
Ask which parts revisions were used in previous repairs and what seals, pipes, belts and coolant were included. Later assemblies can still fail; a facelift or a replacement pump invoice does not excuse current symptoms. An unexplained coolant loss deserves pressure testing and inspection rather than an automatic pump order.
PCV, air-oil separator and intake deposits
FCP Euro’s own PCV procedure places the separator beneath the supercharger and describes the access required. Its symptom list includes rough idle, whistling, oil-consumption and fault-code concerns. These symptoms can have more than one cause, so use the procedure as context for diagnosis, not a reason to order a separator from a single noise.
Ask the garage whether related cooling and ventilation components should be inspected while access is available. Sensible combined work can save duplicated labour, but it should be justified by condition and history. Request an itemised estimate so preventive items are distinguished from confirmed faults.
Direct-injection intake deposits may be relevant when investigating rough running or reduced performance. Establish whether cleaning was carried out, what method was used and whether the symptoms were actually resolved. A carbon-cleaning invoice is not proof that injectors, ignition or compression are healthy.
Tuning and supercharger-drive changes
List ECU and gearbox software, pulley sizes, intake, cooling upgrades and exhaust changes. A pulley modification changes the supercharger’s operating conditions and must be assessed as part of a complete system. Require tuner invoices and clarify the fuel requirement. A dyno result alone cannot establish safe temperatures or current mechanical condition.
During a proper warm road test, check smooth response and investigate misfire, hesitation, surging or unusual noise. Do not accept “all tuned cars do that” as an explanation. Insurance must accept the actual changes, and missing original components should be priced before you plan a return to standard.
S tronic: test it fully warm
The DL501, also called 0B5, is a longitudinal seven-speed wet dual-clutch transmission. It is not interchangeable with every gearbox marketed as DSG or S tronic. Obtain invoices for the correct fluid and filter work and confirm the schedule for the installed transmission with an Audi-aware specialist.
Test forward and reverse selection, slow manoeuvring, gentle changes and normal acceleration both cold and hot. Investigate delayed engagement, shudder, harsh shifts, missing gears and transmission warnings. Restarting the car may temporarily hide an intermittent symptom; it does not prove the underlying problem has gone.
Trescothick Automotive’s DL501 diagnostic account explains that mechatronic, clutch, hydraulic, electrical and mechanical faults can overlap in their symptoms. A fault code directs testing but does not automatically establish which expensive assembly needs replacement. Obtain a written diagnosis before agreeing to buy a car with an unresolved warning.
Manual gearbox, quattro and chassis
On a manual, check clean shifts, clutch take-up and slipping under reasonable warm load. A clutch quote should identify flywheel, release-system, seals and labour scope. Inspect transmission and differential leaks, driveshaft boots and mounts on a lift.
For an optional sport differential, verify fitment and inspect the unit and its controls. Listen for unusual noise and read relevant faults. Do not assume a standard rear differential and the optional system have identical service requirements.
Inspect suspension arms, bushes, dampers, springs, bearings and steering. Adaptive components, if fitted, add their own diagnosis and replacement costs. Check brake wear, caliper operation and fluid history. Pulling, vibration and uneven wear require an explanation supported by inspection and geometry.
Equipment, MMI and everyday checks
Test air conditioning, seat adjustment and heating, MMI, audio, parking equipment, mirrors, lights, windows, locking and both keys. Confirm what connectivity works today; an old brochure’s description of online functions is not a promise of current service availability.
Inspect seat bolsters, pedal wear and luggage-area condition against the claimed use. Check aftermarket wiring and ask about alarms, trackers or audio installations. A low battery can create confusing symptoms, but charging and electrical diagnosis should establish the cause rather than excuse all warnings.
Maintenance and useful parts allowances
Build a maintenance plan from engine and gearbox codes, invoices and inspection results. Use the correct Audi approvals and procedures. A shop’s generic recommendation is not a substitute for the actual build’s schedule, particularly when a tuned car or market-specific component is involved.
These are editorial UK parts-only budgeting allowances, not live offers or fitted quotes. Brand, VAT treatment, exchange surcharges and availability can change the total. Obtain a written fitted quote and check part numbers against your VIN, engine and modifications.
Affiliate disclosure: we may earn a commission from qualifying eBay purchases, at no extra cost to you. The links open vehicle-specific searches; they do not certify the suitability or quality of individual listings. Check seller, fitment, warranty and returns.
| Maintenance item | Parts allowance | What to check |
|---|---|---|
| Oil and filter service parts | £65–£120 | Confirm the correct VW/Audi approval and fill quantity. |
| Spark plugs | £50–£110 | Correct specification depends on engine and verified tune. |
| Alternator | £180–£400 | Check output, application and exchange terms after diagnosis. |
| Starter motor | £120–£280 | Battery, leads, earths and access affect the fitted bill. |
| Supercharger belt | £20–£60 | Pulley changes may require a different belt specification. |
| Accessory belt and tensioner | £60–£180 | Distinguish this from camshaft timing-chain components. |
| Water pump and thermostat | £150–£330 | Compare revisions, seals and pipes; specialist fitting adds substantially. |
| PCV / air-oil separator | £90–£220 | Confirm revision and supporting hoses/gaskets for the actual engine. |
| S tronic service components | £160–£300 | Identify the required circuit, fluid and procedure; not a fault cure. |
| Manual clutch kit | £250–£550 | Manual cars only; flywheel and hydraulics may be additional. |
| Front discs and pads | £180–£380 | Confirm standard or upgraded brakes and the correct dimensions. |
Hidden ownership costs
Access and overlapping jobs: a PCV or thermostat price is only one line in the bill. Supercharger removal, seals, coolant and related inspection can dominate labour. Compare a complete itemised quote and discuss sensible overlap before authorising work.
Gearbox diagnosis: fluid servicing, a clutch repair and a mechatronic repair are different jobs. An apparently inexpensive car with hot shift faults needs diagnosis and a firm repair plan, not an optimistic allowance based on a used part listing.
Four tyres and alignment: budget for a compatible quality set, suitable ratings and geometry. Big wheels, worn arms and poor alignment can turn a new tyre purchase into a recurring expense.
Optional systems: sport differential, adaptive dampers, complex lamps and high-specification audio add repair possibilities. Pay for working equipment that you value, not a list of options the inspection cannot confirm.
Insurance, fuel and tax: quote the individual registration, storage, annual mileage and modifications. A supercharger pulley or gearbox tune must be declared as required by the insurer. Use current registration-specific tax information and your own driving pattern for the running budget.
Downtime and returning to standard: bespoke tuning can need specialist support, software access and original hardware. Check which information and parts transfer with the car, and retain a reserve after purchase rather than using it all to buy a higher output figure.
Eight checks before purchase
- Confirm a supercharged B8/B8.5, body, engine and transmission identity.
- Verify factory options and inspect any sport differential or adaptive suspension.
- Read chronological oil, cooling, PCV and gearbox invoices.
- Arrange a cold start, full warm test and appropriate VAG diagnostic report.
- Investigate coolant loss, rough running and abnormal timing or supercharger noises.
- Test S tronic hot and cold, or inspect manual clutch and flywheel behaviour.
- Inspect body, underside, tyres, brakes, suspension and water ingress on a lift.
- Price the complete fitted work and confirm insurance before paying.
Frequently asked questions
Is the B8 S4 turbocharged?
This generation’s petrol 3.0-litre V6 is supercharged. Earlier V8 and later B9 engine advice should not be applied indiscriminately to it.
Does a gearbox warning always mean failed mechatronics?
No. Clutch, hydraulic, electrical, sensor and mechanical faults can produce overlapping symptoms. Specialist diagnosis should establish the cause before major components are ordered.
Is a facelift automatically trouble-free?
No. Revisions are worth understanding, but the installed parts, maintenance and current condition matter more than the B8.5 label alone.
Should PCV and cooling work always be combined?
Not automatically. Access can overlap, so discuss condition, history and preventive work with the garage. Request an itemised quote that separates confirmed faults from optional work.
Does the engine need a routine timing-belt kit?
The camshaft drive is chain-based. Supercharger and accessory belts still need appropriate checks and servicing, while internal chain concerns require diagnosis.
Research and sources
The repair sources below document work and diagnosis on this engine and transmission family. Their observations are not population-wide failure rates. Parts and model-year differences must be checked against the actual vehicle, and the single price observation is not a broad valuation study.
- FCP Euro: B8/B8.5 water-pump and thermostat procedure: first-hand repair scope, access and component differences.
- FCP Euro: B8 S4 PCV replacement procedure: separator location, diagnostic context and related access.
- Trescothick Automotive: DL501 diagnostic guidance: the distinction between symptoms, fault codes and confirmed repair needs.
- PistonHeads 2013 S4 advertisements: dated Avant asking-price observation, subject to availability and unverified seller descriptions.
