Fault File
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Audi A8

All generations and engines together · 8,385 MOT tests in the 2025 data · typical mileage at age 7: 74k

First-time failure at age 7
8.6%
Across 700 tests. The average across all tracked models is 19.5%.
Rank at age 7
8 of 239
1 = lowest failure rate among the models tracked.
Typical mileage at age 7
74k miles
Check the mileage view below; low-mileage models can look better by age than they are.

Generation

Split by first-registration year. Cars registered in a changeover year can belong to either generation.

How this model wears

Audi A8Class average, all tracked models

Known issues

Measured

Computed from DVSA MOT results, all of Great Britain, 2025. Nothing here is opinion.

What testers flag

Share of tests where each item was recorded. The dark tick is the class average across all tracked models; bars are scaled within each group.

Faults with the car itself

The rows that judge the model rather than its keeper. 3,324 tests in this band.

A suspension pin, bush or joint excessively worn
Advisory
7.3%class 5.9%
Engine MIL illuminated indicating a malfunction
Fail
1.5%class 0.9%
Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users
Advisory
0.7%class 2.0%
A suspension component excessively damaged or corroded
Advisory
0.7%class 0.6%
A suspension pin, bush or joint excessively worn
Fail
0.6%class 0.9%
Excessive fluctuation in brake effort through each wheel revolution.
Advisory
0.4%class 0.6%
Exhaust system leaking or insecure
Advisory
0.4%class 0.6%
An SRS malfunction indicator lamp (MIL) indicates a system malfunction
Fail
0.4%class 0.2%

Wear, upkeep and luck

Tyres, pads and stone chips say more about how the car was driven and maintained than about how it was built.

Tyre tread depth not in accordance with the requirements
Advisory
20.8%class 22.9%
Brake disc or drum excessively weakened, insecure or fractured
Advisory
6.1%class 10.1%
A tyre seriously damaged
Advisory
6.1%class 13.4%
A brake lining or pad worn below 1.5mm
Advisory
5.8%class 8.7%
Brake disc or drum significantly and obviously worn
Advisory
3.7%class 3.4%
Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view
Minor
2.1%class 2.0%
Nail in tyre
Advisory
1.9%class 1.6%
Number plate inscription missing or illegible
Advisory
1.8%class 1.5%

Unconfirmed issues

Reported

Owner folklore from forums and the motoring press. Most of it never shows up in an MOT, which is why this section exists at all.

Sagging air suspension (compressor and struts)

Partly in the MOT data

Adaptive air suspension is standard across the A8 range and the compressor and air struts are the parts owners complain about most, with the car sagging at one corner overnight, warning lights on the dash and rough ride quality replacing the usual wafting comfort. It shows up across D3, D4 and D5 cars and gets more common with age rather than one specific mileage. The measured MOT data backs this up: suspension is the standout fault category for the A8. A full set of struts plus compressor can run well into four figures if it is not caught early.

Reported from 70k miles onward, worsens with age · sources: Honest John owners forum, AudiWorld forums, PistonHeads

3.0 TDI timing chain and tensioner wear (D3, pre-facelift engines)

Emerging

The early 3.0 TDI V6 fitted to the D3-generation A8 has a reputation for a rattly cold start caused by a stretched timing chain or worn tensioner. Audi itself says a couple of seconds of rattle on start-up is within spec, but owners and specialists report cases where it goes on to need the chain and tensioner replaced, and if ignored it can jump timing and damage the engine. It is not officially flagged as a design fault, but it comes up repeatedly on specialist and forum advice for buying an early A8 diesel.

Chain/tensioner issues cluster at high mileage, some cars run well past 150k without trouble · sources: CarChecker, EuroAutoPro, owner forums

Bosch CP4.2 high-pressure fuel pump failure (3.0 TDI)

Emerging

On higher-mileage 3.0 TDI D4-generation cars, the Bosch CP4.2 injection pump can shed metal internally, and that debris then contaminates injectors, fuel lines and the tank. It shows up as a sudden loss of power or a car that will not restart. Because the whole fuel system needs flushing or replacing rather than just the pump, repair bills have been reported running into five figures in the worst cases, though a straightforward pump swap caught early is far cheaper.

Higher-mileage cars, no fixed age pattern · sources: Honest John carbycar guide

8-speed Tiptronic mechatronic failure and wiring loom corrosion

Automatics only

All UK A8s are automatic, but this is worth flagging on its own: the 8-speed torque-converter automatic's mechatronic unit has been reported to fail from around 60,000 miles, and separately the wiring loom to the transmission control unit can corrode after water gets in, which Honest John has priced at close to £5,000 to put right. Symptoms are harsh or delayed shifts, warning lights, or the car defaulting to limp mode.

Mechatronic issues reported from ~60k miles, wiring corrosion needs no set mileage · sources: Honest John carbycar guide

AdBlue/SCR system leaks and warning messages

Disputed

Some D4-generation diesels have been reported to weep AdBlue fluid or throw up SCR system warnings, which can eventually limit engine power or stop a restart if ignored. It is not clear how widespread this is versus normal AdBlue system ageing seen across most modern diesels, and owners disagree on whether it is an A8-specific weak point or just what happens to any high-mileage SCR diesel. Worth checking for AdBlue-related warning history rather than assuming it is unique to this car.

Reported on higher-mileage diesels, no fixed pattern agreed · sources: Honest John carbycar guide

Viewing one? Ask this

Built from the two sections above.

Cycle through the suspension height/mode settings and leave the car standing for 15-20 minutes. Any corner sagging, an uneven stance, or a suspension warning light points to a compressor or strut on its way out.
Start the engine stone cold and listen for a rattle from the front of the block. More than 2-3 seconds of rattle on a 3.0 TDI suggests a worn timing chain tensioner, get it checked before buying.
Ask for a full service history including fuel system work on 3.0 TDI diesels. No record of injector or fuel filter changes on a high-mileage diesel raises the risk of a CP4.2 pump problem developing.
Drive it through low-speed stop-start manoeuvres and check for harsh, delayed or jerky gearchanges. Clunky or hesitant shifts can mean an ageing mechatronic unit or a transmission wiring fault.
Check the dashboard for any AdBlue or SCR warning messages during the test drive. An active or recently-cleared AdBlue warning is worth asking the seller about directly.
Pull the full MOT history rather than just the pass/fail summary. Repeated suspension advisories in the same spot mean a worn part has been patched rather than properly fixed.
Get a specialist to plug in a diagnostic reader before buying. Cleared fault codes can hide a suspension, gearbox or AdBlue problem that will reappear within weeks of purchase.

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