Audi S6 (C6) V10
Why 6.5: DougScore 56 for a V10 Audi borrowed from the Gallardo parts bin and never repeated in another S6 — every generation before or since used a V8 or a turbocharged six. Values have fallen off a cliff since, turning a genuinely exotic-adjacent drivetrain into one of the cheapest ways to own a Lamborghini-related engine.
Layout
Natural habitat
Ride comfort
Sound
The 5.2 shares its architecture with the Gallardo and starts with the same ten-cylinder churn, then holds a clean naturally aspirated wail to 7,000 rpm. But Audi buried it under saloon insulation and a quiet exhaust, so you get the timbre without the volume.
10-cylinder · naturally aspirated · 7,000 rpm redline · rated 7.9 / 10 for engine sound
Market value
Median asking price, good condition · €71k (2008) → €16k (2026), trending down · illustrative data
Child seats · ISOFIX
Both outer rear seats carry ISOFIX anchorages per the same manual — no centre-rear anchorage is mentioned.
Audi's own A6 (C6) owner's manual states ISOFIX anchorages are fitted on the front passenger seat as well as both outer rear seats; UK C6 owners on the TyreSmoke forum independently confirm all three positions.
S6 shares the A6 C6's seat shells; the optional S-line sport seat isn't separately confirmed to retain the anchors, though it's an Audi in-house part rather than an aftermarket bucket.
Audi A6 (C6) Owner's Manual; TyreSmoke A6/S6 C6 owner forum
The long version
The C6-generation S6 borrowed its naturally aspirated V10 from the Gallardo parts bin, detuned and reworked for a Tiptronic automatic and quattro all-wheel drive, and Audi never repeated the experiment — every S6 before and after has used a V8 or a turbocharged six. That drivetrain came with genuine complexity: timing-chain and tensioner problems earned the V10 a reputation that tanked resale even faster than a big, thirsty sedan usually manages, and today's used market treats it as a cautionary tale rather than a Q-ship curiosity. The buyers who do own one tend to know exactly what they're getting — a Lamborghini-adjacent engine note in a practical AWD sedan, bought at a price that assumes a major service bill is coming and driven hard enough to justify the risk. It's the Bargain Window case study for engine snobs: nothing else gets you this specific V10 for this little money.