A 2011 to 2018 C7 Audi A6 2.0 TDI with cambelt receipts and no DPF warnings since its emissions fix is the lesser risk; avoid the 2004 to 2008 2.0 TDI PD, whose oil pump drive can wreck the engine.
26 known faults, 23 rated high severity in our database; owners report 40.8 mpg, 83% of the official figure. Everything below is built from that data and the archived owner history, not from a press car.
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Check an Audi A6 advert (free) →The 2011 to 2018 C7 with the 2.0 TDI is the A6 carrying the least engine risk, because its known faults are about the emissions software update, gearbox judder and electrics rather than parts that wreck the engine. That doesn't make it a free pass: owners have reported DPF warnings and blocked EGR valves after the update, so watch for those warning lights on the drive.
Pick a 2004 to 2011 C6 more carefully. Its 2004 to 2008 2.0 TDI PD has a known oil pump drive fault that strikes between 60,000 and 100,000 miles and destroys the engine, and the 2.7 and 3.0 V6 TDIs and the 3.2 FSI petrol all have known timing chain failures. Those chains sit at the back, so the engine has to come out to reach them. The oil pump and injector faults belong to the older PD engine, not the common-rail 2.0 TDI that arrived in 2009.
The 1997 to 2004 C5 has a known fault with blocked bulkhead vent drains letting water into the cabin and upsetting the electrics, and Allroads from 2000 to 2006 have known air suspension leaks. The newest A6, on sale from 2018, has only a few notes, mainly that its eight-speed auto can be slow to respond, but fewer reports aren't proof it's sorted, and the known 3.0 V6 TDI chain tensioner fault runs up to 2018.
The common-rail 2.0 TDI in the C7, and in C6 cars from 2009, is the lesser engine risk, as long as you check how it's coped with the emissions update. A flashing glow plug light, limp mode, frequent DPF warnings or revs sitting 200 to 300rpm higher than before all point to known EGR and DPF trouble since the software fix. Its cambelt is listed at 60,000 miles or 60 months, so ask for the receipt.
Avoid the 2004 to 2008 2.0 TDI PD. The small hex shaft that drives its oil pump from a balancer shaft is a known fault that rounds off between 60,000 and 100,000 miles, and when it goes, oil pressure vanishes and the engine and turbo are ruined. One owner had theirs fail twice, 30,000 miles apart, and paid £3,500 to an independent the first time. On 2006 to 2009 PD engines, check the injector recall's been done; the cambelt is listed at 75,000 miles or 60 months.
The 2.7 and 3.0 V6 TDIs carry bigger risks. Both have known timing chain failures, and the 3.0's tensioners are listed as going between 80,000 and 140,000 miles; the 3.0 TDI also suffers water pump failures and coolant loss from its water-cooled EGR valve from 95,000 miles, and the 2.7's swirl flap motors fail. The 3.2 FSI petrol's chains have failed too, especially on Longlife servicing, and a 2.0 TFSI from 2008 to 2013 can rattle on cold starts as its chain tensioners fail, ending in a rebuild.
The Multitronic CVT is the gearbox to avoid: front-wheel-drive autos from 2004 to 2012 wear their clutch packs or lose their control units between 60,000 and 100,000 miles, and it wants oil and a filter every 40,000 miles. Manual 2.0 TDIs aren't clear either, with a known flywheel fault that brings stalling and clutch failure, often by 45,000 miles. The 3.0 TDI's seven-speed S tronic judders in first and reverse, and its oil's due at 35,000 miles, then every 40,000.
Hear the engine start from cold, as several serious A6 faults begin as a rattle. A metallic slapping from the back of a 3.0 V6 TDI that lasts more than three seconds points to its chain tensioners, the 2.7 TDI and 3.2 FSI rattle at the rear when their chains are failing, and a 2.0 TFSI from 2008 to 2013 that rattles at start-up points to failing tensioners. Check a 3.0 TDI's coolant level, and don't touch a 2004 to 2008 2.0 TDI with a red oil pressure light.
On the drive, a Multitronic that shudders from rest, flashes its PRNDS display or refuses to leave park is on its way out, and one that revs without moving when pulling uphill from cold before lurching forward shows a known fault. In a manual 2.0 TDI, feel for judder pulling away and for stalling. With a 3.0 TDI S tronic, try first and reverse once it's warm, on a slope if you can, as clutch judder there is a known fault.
Lift the panel on the nearside of the boot in a 2004 to 2011 Avant and look for water, since the rear washer pipe can leak onto the MMI unit, then test the sat nav, phone and radio. Check the footwells of a C5 for damp and see if the brake pedal feels hard. Raise an Allroad's suspension to full height and watch for a corner sagging, and on a 2012 to 2018 Allroad look for damp headlining around the panoramic roof.
Ask for receipts for the cambelt and for Multitronic or S tronic oil changes, plus proof of the recall work: new injectors on 2006 to 2009 2.0 TDI PD cars, and the software update that shuts down a blocked extra coolant pump on 2007 to 2017 2.0 TFSI engines. On a C7, try the adaptive cruise and check the sat nav shows the right location, as both have failed together, with the sat nav fault traced to water in the shark's fin aerial.
Paste the advert into the free check and it runs these against the listing, the MOT history and the DVLA record before you travel.
The C5's known weak spot is water: when the bulkhead vent drains clog with leaves, rain ends up in the cabin and causes electrical faults at any mileage. On petrol cars that water can rust through the brake servo, leaving a rock-hard pedal, and even get drawn into the engine and hydrolock it. Lift the carpets to feel for damp and check those drains are clear, as they're meant to be cleared out regularly.
The 1.8 20v petrol has snapped its cambelt at 70,000 to 80,000 miles, which kills the engine outright, so don't buy one without proof the belt and tensioner have been done; its air mass sensors have failed, and the turbo's ignition coils. Owners have reported heavy oil use from the 2.4 V6. The 2.5 V6 TDI's cambelt is listed at 60,000 miles or 48 months, and its Multitronic got a revised seven-plate clutch under a 2005 service bulletin because the original couldn't cope with the torque.
The Allroad's height-adjustable suspension makes it surprisingly able off-road, but air suspension bladders on 2000 to 2006 cars are a known failure: they're built into the struts, often leak once raised to the high setting, and replacements don't last long. Raise it to full height and see if a corner drops, and check underneath for off-road damage. The RS6's gearbox is a known failure after 50,000 miles, its Dynamic Ride Control dampers leak, and one S6 owner needed a new tiptronic gearbox at 28,000 miles.
Its tiptronic lever works back to front, pushed forward to change up. Any accident repair deserves a close look, as panels that weren't galvanised or badly welded ones rust, and test the driver's electric window and the front passenger door lock, which have both failed. Ask for proof of the recalls to replace track rod ends on 1999 model year cars and the free front axle bellows check on 1997 to 1999 cars.
Real-world economy on this generation: Audi A6 39.5 mpg.
The C6's worst known fault is the oil pump drive on 2004 to 2008 2.0 TDI PD engines, which rounds off between 60,000 and 100,000 miles and takes the engine and turbo with it. One owner's 60,000-mile Avant lost its oil pump and turbo, and because it had a full Audi dealer history, the bill came to £1,000 after Audi and the dealer chipped in. Audi wouldn't help another owner whose car had been serviced independently.
Manual 2.0 TDIs have a known dual-mass flywheel fault that brings stalling and clutch failure, often by 45,000 miles, while 2.0 TDI Multitronics stall on descents and at low speed, and their EGR valve can snap a weld and lose power with a noise. Front-wheel-drive Multitronics from 2004 to 2012 wear out their clutch packs and suffer control unit failures between 60,000 and 100,000 miles. The 2006 to 2009 2.0 TDI PD engines were recalled for injectors that could short out and cut the engine.
The 3.0 TDI has known water pump failures and coolant loss from its water-cooled EGR valve from 95,000 miles, and some owners have seen it use a litre of oil every 1,000 miles. On the 2.7 TDI, swirl flap motors in both inlet manifolds fail and individual flaps can break, though none's been reported going into the engine; one 2.7's timing chain failed at 118,000 miles. The 3.2 FSI's chains have failed on Longlife servicing, and one 2009 2.0 TFSI's chain went at 98,000 miles.
Avants have a known leak from the rear washer pipe onto the MMI unit in the nearside of the boot, which kills the sat nav, phone and radio, and there's a service bulletin for the hose repair. On a 2006 to 2012 Allroad, check the aluminium trim along the door bottoms for oxidising, which shows within three years, and look for leaks from the rear air suspension dampers, which have been reported leaking after about six years. The C6 scored five stars for crash protection.
Real-world economy on this generation: Audi A6 39.5 mpg, Audi A6 Avant 38.3 mpg, Audi A6 Allroad 34.3 mpg, Audi A6 42.6 mpg, Audi A6 Avant 41.6 mpg.
The C7's known faults hit the 3.0 V6 TDI hardest, with camshafts and timing chain tensioners needing an engine strip-down between 37,000 and 77,000 miles on 2012 to 2018 cars. One high-mileage Allroad had a camshaft repaired under warranty at 37,000 miles, then needed its tensioners at 77,000, by which point the car was out of warranty and the second strip-down was the owner's to pay for. Another 2015 Allroad was reported as needing four new camshafts at 40,000 miles.
With the 3.0 TDI, the S tronic has a known judder in first and reverse from 10,000 to 30,000 miles, worst when it's warm or on a hill. Multitronics can rev without moving when pulling uphill from cold, then lurch or stall, even after fresh fluid, a known fault seen at 60,000 miles. Manual 2.0 TDIs have a known drivetrain judder blamed on the flywheel; one owner paid £120 just for the first diagnosis, and another was left with a £4,000 bill when a manual gearbox failed at 80,000 miles.
The 2.0 TDI's emissions update is a known sore point, with owners reporting higher revs, more fuel used, frequent DPF warnings and blocked EGR valves afterwards. There are also reports of total electrical failure while driving, one losing steering and brake assistance at 70mph and another carrying straight on when its wheel was turned, plus a known fault where adaptive cruise and auto braking quit together while water in the shark's fin aerial throws the sat nav location out.
Panoramic sunroofs on 2012 to 2018 Allroads have leaked even with clear drains, so check for a damp headlining. Test the audio too, since an amplifier failure has knocked out one owner's radio and Bluetooth after a central locking repair. The 2.0 TFSI's extra coolant pump was recalled on 2007 to 2017 engines, and one 2012 car burned a litre and three quarters of oil in 5,800 miles. The C7 has a five-star crash rating.
Real-world economy on this generation: Audi A6 42.6 mpg, Audi A6 Avant 41.6 mpg, Audi A6 Allroad 38.9 mpg, Audi A6 44.4 mpg, Audi A6 Avant 47.5 mpg.
Sellers rarely admit these faults outright
Paste any Audi A6 advert and we check it against the faults, the MOT record and these figures in seconds.
Check an advert now (free) →Owners report 40.8 mpg across the Audi A6 engines with data, about 83% of the official figure, from 1,966 submissions.
Audi A6 Real MPG by engine →The C5 is a handsome car with soft handling that never feels floaty, and it grips decently through bends. The first Allroad has a classy look of its own, and the 2006 to 2012 Allroad is very comfortable, whether you're on tarmac or a rough track.
The 2012 to 2018 Allroad's ride is smooth and refined, and its interior's finished to a very high standard. The newest A6, from 2018, has a premium cabin with plenty of space, and there's more room inside than there was in the car it replaced.
A 2011 to 2018 C7 Audi A6 2.0 TDI with cambelt receipts and no DPF warnings since its emissions fix is the lesser risk; avoid the 2004 to 2008 2.0 TDI PD, whose oil pump drive can wreck the engine. Our database holds 26 known Audi A6 faults, 23 rated high severity, and the sections above say which generation and engine carry them.
The 2011 to 2018 C7 with the 2.0 TDI is the A6 carrying the least engine risk, because its known faults are about the emissions software update, gearbox judder and electrics rather than parts that wreck the engine. On the fault record the C5 (1997 to 2004) carries 4 known faults against 12 on the C6 (2004 to 2011). Each generation's section above gives the detail. Audi A6 faults by generation.
Hear the engine start from cold, as several serious A6 faults begin as a rattle. Read the MOT history for repeat advisories and ask for invoices for any work the seller mentions. Then paste the advert into the free check, which reads it against every known Audi A6 fault before you travel.
Owners report 40.8 mpg on average, about 83% of the official figure, from 1,966 submissions. Belt (2.0 TDI, EA189, EA288): 60,000 miles or 5 years, whichever comes first, so budget for it if the history does not show it done. The known faults page lists a rough repair cost against each fault. Audi A6 Real MPG by engine.
If you used the Honest John car-by-car reviews before the site closed in 2026, this is where the Audi A6 buying advice now lives. It is written from the archived owner reports and model notes (archived page, 154 items read for this model), our own known-faults database, the confirmed service intervals and the Real MPG figures. Every number on the page comes from that data, not from the text. The same data feeds our free advert check.
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The Audi A6 is one decision. Reading the advert, the history and the seller are the rest, and these cover them.
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