Audi A6 C8 Review: Problems, Engines and Servicing

If you're looking for an Audi A6 C8 review, chances are you're thinking about buying one used. And I can understand why. The Audi A6 C8 (4A), produced since 2018, is a modern, comfortable car packed with technology. But the bigger question is: what does it cost to maintain, and how much trouble could it give you? At Das Auto Service, we see how these cars hold up as the mileage climbs. I'll explain what we check, where problems tend to appear and what I'd look for before buying one myself.

Who is the Audi A6 C8 right for?

If you want a large, modern car with plenty of technology, driver assistance features and comfort, the A6 C8 is definitely worth considering. But this isn't a car where you can neglect servicing and expect everything to keep working perfectly. There are lots of electronic systems that need to communicate properly with each other. And when something goes wrong, the cause isn't always where you'd expect. That's why I say the A6 C8 is for someone who appreciates technology but understands that it needs looking after.

What engines and gearboxes does the Audi A6 C8 have?

The A6 C8 comes with a choice of four-cylinder diesel, V6 diesel and petrol engines. The differences aren't just about how the car drives. They also affect the gearbox, drivetrain and the systems you'll need to maintain. Here are the main versions we look at.

• 40 TDI – 2.0 TDI diesel engine with a 7-speed S tronic automatic gearbox.
• 45 TDI and 50 TDI – 3.0 TDI V6 diesel engines with an 8-speed Tiptronic gearbox and quattro all-wheel drive.
• 45 TFSI and 55 TFSI – petrol versions, with the 55 TFSI using a V6 engine.
• Mild hybrid – 12 V system on four-cylinder engines and 48 V on V6 engines.

I wouldn't choose an engine just by looking at the badge on the boot. What matters is how that particular car has been maintained, how the gearbox behaves and whether all the electronic systems work properly. Two cars with exactly the same engine can be in completely different mechanical condition. That's why the service history and diagnostic results matter far more than the nice photos in the advert.

What problems do we see in our Audi A6 C8 review?

Mild hybrid system

One system we pay particular attention to is the mild hybrid system. It includes a belt-driven starter-generator and a lithium battery, and faults can show up in different ways. You might see fault codes, the Start/Stop system might stop working, or the car might not pull away smoothly. That doesn't mean you should immediately start replacing parts whenever you notice one of these symptoms. First, you need to find out what's actually causing the problem. I've covered this in detail in Audi A6, A7, A8 and Q7 48 V mild hybrid system.

AdBlue and DPF problems on diesel engines

On diesel versions, we pay close attention to the AdBlue system and the condition of the DPF (diesel particulate filter). If the car is mainly used for short journeys around town, the filter can start to clog up. The owner then sees a warning light on the dashboard and wonders how serious the problem is. The truth is, without proper diagnostics, you can't know exactly what's happening. Simply clearing the fault code and carrying on isn't enough.

MMI, cameras and driver assistance systems

The two MMI screens look impressive, but there's software behind them that can also cause problems. Then there are the cameras and radars that the driver assistance systems rely on. After a windscreen replacement or an accident, you need to check whether calibration is required and carry it out if necessary. This isn't just about clearing fault codes. These systems need to recognise what's happening in front of the car correctly.

Air suspension

If you're looking at an A6 C8 with air suspension, pay attention to how the car sits after it's been parked for a while. If one side has dropped or the whole car is sitting unusually low, that's a sign something needs checking. Another symptom is a compressor that runs for an unusually long time. I wouldn't consider that normal just because the car eventually raises itself again. You need to find the cause before deciding whether to buy it.

What should I check before buying an Audi A6 C8?

With this model, simply plugging in a diagnostic tool and checking the engine isn't enough for me. I want to see the condition of every electronic control module because problems aren't always engine-related. These are the checks I pay particular attention to.

1. A full diagnostic scan of every control module, not just the engine.
2. Check the mild hybrid system, stored fault codes and battery condition.
3. Check the AdBlue system and DPF on diesel cars.
4. Check the driver assistance systems, how they operate and whether they're correctly calibrated.

All of this is included in our pre-purchase inspection. For me, this isn't just a box-ticking exercise. It's how you find out what you're actually buying. A car can look spotless on the outside while the diagnostic results tell a completely different story.

How should I service my Audi A6 C8?

With a modern Audi, proper servicing matters more than ever. Don't wait for a warning light before thinking about visiting a workshop. Here are the service intervals I recommend for cars driven in Bulgaria.

• Engine oil and filters – every 10,000 km or once a year, whichever comes first, regardless of the LongLife service interval. The oil must meet the correct manufacturer specification for your particular engine.
• S tronic – change the gearbox oil every 60,000 km, always using genuine oil.
• Tiptronic – every 120,000 km on Audi A models, and every 80,000 km on S, RS and hybrid versions. We always carry out a gearbox adaptation after servicing.
• Brake fluid – every 2 years.
• Coolant – every third heating season.
• Preventative workshop inspection – every 6 months.

If you drive the V6 diesel version, you can also read our detailed Audi A6 C8 3.0 TDI service schedule. The right service interval and the right oil go hand in hand. There's no point changing your oil on time if you're using a product that doesn't meet the correct specification.

Is a used Audi A6 C8 worth buying?

My view is that the Audi A6 C8 is an excellent car, provided you know what you're buying. I want to see a service history, a full diagnostic scan and properly checked driver assistance systems. If everything is in good order, you're getting a large, modern car with plenty of technology and comfort. But if you rely only on how it looks and a quick test drive, you could be buying yourself some very unpleasant surprises. In my opinion, a pre-purchase inspection is essential with the C8.

Tip from Kris Mladenov: Before you spend money on a modern Audi, spend some on a full diagnostic scan of every control module. Check the service history, mild hybrid system and driver assistance features instead of relying on how the car looks and drives. It's one of the smartest checks you can make before buying.

I hope you've found this article useful! If you have, I'd appreciate you sharing it with a friend who's looking at an Audi A6 C8. My mission is simple: when I know something, I want more people to know it too. That way, more owners can make informed decisions and look after their cars properly.

The solution in our shop

Genuine LongLife IV 0W20 oil G S60577M2 1l

Genuine LongLife IV 0W20 engine oil for engines that require this viscosity and the corresponding oil specification. Only use it when specified for your particular engine.

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Genuine VAG AdBlue® fluid G052910M4 10l

Genuine AdBlue in a 10-litre container for diesel versions equipped with an AdBlue system.

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Genuine Audi/Volkswagen DOT 4 brake fluid B000750M3 1l

Genuine DOT 4 brake fluid for brake system servicing.

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Read more

• Pre-purchase inspection
• ACC and driver assistance calibration
• Audi A6 C8 3.0 TDI Service Schedule
• Audi 48V Mild Hybrid Problems: A6, A7, A8 and Q7

Frequently asked questions

What maintenance does the Audi A6 C8 need?

We change the engine oil and filters every 10,000 km or once a year, and the S tronic gearbox oil every 60,000 km. For Tiptronic, the interval depends on the version. I also recommend a preventative workshop inspection every 6 months.

What are the most common Audi A6 C8 problems?

We pay particular attention to the mild hybrid system, AdBlue and DPF on diesel models, MMI, driver assistance systems and air suspension. Not every car develops these problems, which is why a full diagnostic scan is so important.

Audi A6 C8 40 TDI or 50 TDI – which should I choose?

The 40 TDI has a 2.0 TDI engine and a 7-speed S tronic gearbox, while the 50 TDI has a 3.0 TDI V6, an 8-speed Tiptronic gearbox and quattro all-wheel drive. I'd make my choice based on the car's mechanical condition, service history and diagnostic results.