Audi A8
4.2-litre TDI V8 with 350 PS — revised V8 diesel generation. More reliable than the D3 predecessors; timing chain elongation still possible with neglected servicing. Watch for intake manifold and throttle body issues. Fixed oil change intervals of 10,000 km; Longlife oil not recommended.
Smooth multi-cylinder — effortless touring
351 hp 4.2L with pleasant refinement. Relaxed cruising, no sporting ambitions. Budget for the known weak points.
Engine Weaknesses 6
The 4.2 TDI V8 in the A8/Q7 variant (CDLA) also shows timing chain wear. Tensioners and guide rails wear; rattling on cold start is an early warning. Replacement 3,000–6,000 €.
Symptoms: Rattling on cold start, progressively louder noise at higher rpm, engine warning light
Both turbochargers on the 4.2 TDI V8 in the A8/Q7 are subject to heavy thermal stress. Actuators and the VTG mechanism fail, especially at higher mileage.
Symptoms: Power loss, limp-home mode, boost pressure fault codes, soot particles in the intake
Piezo injectors on the 4.2 TDI V8 show wear and leakage at higher mileage. Eight injectors increase the risk; complete set renewal costs 3,000–6,000 €.
Symptoms: Misfires, fault codes on individual cylinders, engine stuttering, rough idle
4.2 TDI V8 CDLA uses a complex four-chain timing drive (one per cylinder bank, a connecting chain, oil pump). Full replacement takes 15–20 hours, cost approx. €3,000 for chains alone.
Symptoms: Rattling on cold start, engine warning light, timing sensor faults
V8 TDI variants can also be affected by camshaft material defects. The result is engine damage. Repair costs are higher than for the V6 due to the larger size and complex disassembly.
Symptoms: Unusual knocking noises, power loss, engine warning light
The ZF Tiptronic gearbox in the A8 4.2 TDI is known to be problematic. Juddering on pull-away, shift delays and the gearbox oil schedule (every 60,000 km) are often neglected.
Symptoms: Juddering on pull-away, delayed or harsh shifting, slip feeling on gear changes
Vehicle Weaknesses 13
The adaptive air suspension on the A8 D4 is a well-known money pit. Air bellows become porous, the compressor runs non-stop and overheats. Repairing all four corners costs several thousand euros.
The 4.2 TDI V8 in the A8 D4 has a timing chain that is prone to premature wear when neglected. A break causes severe engine damage. Replacement requires complete engine removal.
The 4.2 FSI V8 has four timing chains with phenolic resin guide rails that become brittle with age. Neglected oil changes risk chain skip.
Turbocharger bearings can wear and bring the turbine wheel into contact with the housing. Audi recalled around 26,000 vehicles in 2022.
Leaking air bellows cause the vehicle to sink and force the compressor into continuous operation until it fails. Front and rear are equally likely to be affected.
The MMI multimedia system stands out from 60,000–100,000 km with frozen screens and unresponsive controls. Multiple control modules can be affected.
The ZF 8-speed automatic shows harsh gear changes and gear selection problems at high mileage. Regular oil changes (every 80,000 km) are critical.
The MMI multimedia system is known for total failures caused by overvoltage damage after battery replacement or moisture damage to the Bluetooth control module.
The rubber-metal bushes of the front control arms on the heavy A8 D3 show significant wear at high mileage.
Front and rear control arm rubber bushes go soft with increasing mileage. The A8's considerable weight accelerates wear.
The 6-speed Tiptronic shows harsh gear changes at high mileage. A gearbox oil change often resolves the problem.
With increasing age the driver's side window regulator switch block on the A8 D3 frequently fails. The switch block must be completely removed for replacement. Pixel failures in the instrument cluster and screen faults are further typical age-related symptoms.
Almost all A8 D3s show worn and peeling soft-touch surfaces on light switches, trim panels and control knobs. The coating detaches in strips, leaving a sticky surface that is visually badly affected.
Reports & Tests
124 owner complaints filed with NHTSA (2010–2017). Most reported: Engine (78), Other (13), Fuel System (12).