IsItAGoodCar
Reliability Guide

Common Problems with the
2018 Audi Q8 (4M8)

The launch year brought Audi's largest and most complex SUV coupe. Early 2018 cars carry a higher risk of 48V mild-hybrid BSG failures and MMI software glitches, so check recall status carefully.

What changed for 2018

  • •Launch with 3.0 TFSI and 3.0 TDI engines
  • •Standard 48V mild-hybrid system
  • •Dual-touchscreen MMI interface
  • •Air suspension standard on most trims

Common MOT watch-outs

  • !48V BSG alternator failure at 20k–60k miles
  • !Air suspension strut leaks
  • !Infotainment screen freezing and reboots
4
Known Issues
3
Serious
1
Moderate
0
Minor

All Known Issues

48V Mild Hybrid System Faults

SeriousElectrics & Electronics

The belt-starter-generator can fail, disabling start-stop and energy recuperation, and potentially stranding the car when both batteries drain.

Est. Repair Cost: £0 (recall) – £1,500
Warning Signs:

Electrical system malfunction warning, Start-stop inactive, Rough engine restarts

What to Inspect:
  • Check for completed recall or service campaign work
  • Scan for 48V system fault codes
  • Verify battery health
Verified by IsItAGoodCar Research Team

Adaptive Air Suspension Leaks

SeriousSuspension & Chassis

The air springs can develop leaks causing uneven ride height, and the compressor burns out trying to compensate.

Est. Repair Cost: £800–£2,500
Warning Signs:

One corner sitting low after parking, Compressor running constantly, Air suspension warning light, Bouncy ride

What to Inspect:
  • Inspect ride height after standing overnight
  • Cycle suspension through height settings
  • Listen for compressor strain or hissing from wheels
Verified by IsItAGoodCar Research Team

TDI SCR / AdBlue System Faults

SeriousExhaust & Emissions

Diesel versions with SCR can develop dosing, heater or NOx sensor faults. A system fault may lead to a no-restart countdown even with sufficient AdBlue; diagnosis should distinguish fluid level from component failure.

Warning Signs:

AdBlue system warning, No-restart countdown

What to Inspect:
  • Check warning history and emissions repair invoices
  • Request a diagnostic check of dosing pressure, heater operation and NOx readings
Verified by IsItAGoodCar Research TeamUpdated

Infotainment and MMI Freezing

ModerateElectrics & Electronics

The dual-touchscreen MMI system can freeze, go black, or reboot spontaneously, affecting climate and vehicle controls.

Est. Repair Cost: £0–£900
Warning Signs:

Frozen or black screens, Climate controls unresponsive, Navigation or media dropouts

What to Inspect:
  • Test both touchscreens extensively
  • Check software version and update history
  • Verify no persistent error messages
Verified by IsItAGoodCar Research Team

Buying Tips for 2018 Audi Q8 (4M8)

  • ✓Verify the 48V BSG recall campaign has been completed
  • ✓Check both MMI touchscreens for lag and dead spots
  • ✓Inspect large alloy wheels for kerb damage — replacements are very expensive
2019–2021
Check a 2018 Audi Q8 (4M8) by Registration