The larger diesel found across A6, A7, Q5 and Q7 — widely regarded as one of the more dependable engines in Audi's modern lineup, with a short, well-documented list of known issues.
This engine has a stronger reputation than the smaller four-cylinder TDIs, largely because it isn't worked as hard relative to its output. The main points of failure are mechanical and well understood rather than emissions-related: a timing chain tensioner that can fail if oil changes slip, and swirl flaps on earlier versions. Properly serviced, six-figure mileages with no major work are common.
Not a guarantee, but a pattern seen consistently across owner forums and independent-garage reporting.
Swirl flap issues (pre-2014 units) if the engine has had infrequent intake cleaning.
Timing chain tensioner wear becomes the main watch item, especially on cars with extended oil-change intervals.
Core bottom end remains strong; most reported failures at this stage are ancillary, not structural.
Ask for proof of oil-change intervals specifically — this engine is more sensitive to stretched intervals than most, because of the tensioner's reliance on consistent oil pressure.
Listen for a rattle on cold start that doesn't clear within a couple of seconds — unlike the EA888's brief tensioner tick, a persistent rattle here is worth walking away from without inspection.
On pre-2014 cars, ask whether the swirl flaps have ever been removed or replaced — a common and relatively cheap preventative job.
Model-specific pages, with notes on how it behaves in that particular car.