Modern A6 diesels are Euro‑6 engines with DPF and usually an AdBlue system; they reward steady, longer runs rather than lots of short city trips. Audi fit either 7‑speed dual‑clutch (S tronic) on smaller units or 8‑speed torque‑converter autos on larger TDIs, so check which gearbox this car has because service and fault types differ. Parts and dealer servicing are widely available in Ireland but can cost more than mainstream small cars.

• DPF / regeneration history — ask whether the car has regular long runs and check for warning lights or frequent DPF-related repairs
• AdBlue level system and any warning codes; AdBlue faults can immobilise emissions control if neglected
• Automatic gearbox behaviour and service history — verify smooth upshifts, no jerking or hesitation, and confirm transmission oil/service schedule (S tronic vs tiptronic differences)
• Turbocharger and smoke on acceleration — watch for excessive blue/black smoke and check for oil leaks around turbo and intercooler pipes
• Suspension: listen for knocks and check for uneven ride or compressing (air suspension if fitted can develop leaks or compressor faults)