2018 (68) Audi A6 40 TDI Sport 4dr S Tronic

By Jonathan Crouch

Introduction

Smart, relatively light, suitably fast and quite green, Audi's C8-series A6 model, which sold between 2018 and 2025, offers a beautifully conceived and expertly executed alternative for buyers in the full-sized Executive sector currently considering saloon or estate versions of cars like BMW's 5 Series, Mercedes' E-Class or Jaguar's XF. The use of front wheel drive at the foot of the range still differentiates this contender from rivals like these, but with this model, Ingolstadt claimed a new level of dynamic parity in other regards. There was certainly no doubt that this C8-era was thoroughly rejuvenated over its predecessor, with mild hybrid engine technology, class-leading possibilities for driving autonomy, sophisticated media connectivity and cutting-edge cabin design. All delivered along with the kind of ownership and running costs that played well in the practically-minded fleet market. In short, if you're browsing for a full-executive premium badged saloon or estate from this period, this A6 is a difficult car to ignore.

History

While Audi's A6 has long been the world's best selling full-sized Executive car, it's rarely been Britain's overall favourite. By 2018, Audi had offered no fewer than eight different models in this segment and with this C8-series design, the fifth of them to be badged 'A6', there were fewer reasons than ever not to consider one. Whether you choose this design in saloon form or the alternative Avant estate body style, this sleeker more sophisticated C8 design proved to be quieter, lighter, smarter and more technologically advanced than its predecessor. By the time of this C8 model's launch, the Ingolstadt brand had been making full-sized Executive segment business-orientated saloons and estates since 1968, changing the badge work from 'Audi 100' to 'Audi A6' in 1994 but keeping the same Teutonically clinical approach to wafting middle-aged company folk between far-flung boardrooms. All the while though, the German brand had been refining its approach, first with the C5-series model in 1997 and then with the more sophisticated C6-series design of 2004 and the C7-series model launched in 2012. The C8-series A6 design we're looking at here was introduced in mid-2018 and is, as you would expect, was a much more modern interpretation of the breed. The petrol and diesel engines used became much more efficient thanks to MHEV mild hybrid electrification and the new-era cabin became completely touchscreen-orientated. In addition, the sleek exterior styling introduced a fresh design language for this model line and clothed a completely new and much stiffer aluminium-intensive MLB EVO body structure. Options from new included four-wheel steering and an astonishingly sophisticated active air suspension system. And Audi engineered this contender to be able to offer so-called 'Level 3' autonomous driving tech, which theoretically allowed its driver not only to relinquish control at certain speeds but actually to engage in other tasks unconnected with driving. In short, it was all very Vorsprung Durch Teknic. In 2019, the A6 range expanded with an allroad Avant estate model (which lasted only two years); and a flagship RS 6 Avant high performance flagship variant (which lasted until the end of C8 production). A PHEV 50 TFSI e model arrived in 2020. There was a light facelift in 2023 which saw the main A6 range through to the end of production in late 2024; it was replaced by a new generation C9-era A6 in early 2025.

What You Get

According to Audi's research clinics, A6 customers value understated exterior design above almost everything else - so they should feel right at home with the conservatively evolved looks of this C8-series eighth generation contender. Whether you choose saloon or Avant estate, the balanced proportions are smart and contemporary, with much borrowed from this model's A8 saloon and A7 Sportback stablemates. That means taut surfaces, sharply defined edges, striking lines and short overhangs. This is a pretty sizeable piece of sculpted Executive segment German real estate, being nearly five metres long and the best part of two metres wide, yet standing only just over 1.4-metres high. Classically elegant? Maybe not, but it's certainly handsome and sophisticated, with shaping that the brand reckoned referenced its 'quattro genes'. The Avant version is exactly the same length as the saloon but is 10mm taller. Behind the wheel, the Vorsprung Durch Teknic charisma of this car really gets into gear. There's a different, more technological ambiance than you get with obvious rivals, but the interior still incorporates the required splash of luxury needed for a full-sized Executive model of this status. You're going to need to like screens because the completely redesigned cabin can incorporate no fewer than three of them, largely replacing all the many buttons and dials of the previous A6. The two you'll notice first power up as soon as the door is opened and dominate the upper and lower parts of the piano black-trimmed centre stack. The gently curved upper display deals with the most important radio, media and telephone functions while the lower 8.6-inch monitor is reserved for more comfort-orientated mainly climate-related features. Both monitors interact with the optional 12.3-inch 'Audi Virtual Cockpit' instrument binnacle screen you view through the three-spoke wheel. In the rear, thanks to 21mm of extra interior length over the old C7 model, a 6ft 3-inch passenger can comfortably sit behind a driver of the same size. Audi said that with this C8 design, legroom in the back increased by 17mm, while headroom was up by 10mm. Out back, the boot is the same size as it was with the previous generation design, which means that it's pretty big. Raise the wide-opening lid and you'll find 530-litres in all. If you need more room, the trunk can be extended by flipping forward standard split-folding rear seats - a feature that cost extra on rival BMW and Mercedes models. The extra space this feature frees up may be enough to preclude some from having to consider the greater capacity of the Avant estate version. If not, then in an Avant, once you've raised the standard electric tailgate, you'll find 565-litres of space.

What to Look For

Not too much goes wrong with a C8-era A6. The most common issue we've heard of relates to excessive oil consumption for models with the 2.0 TFSI petrol engine. The 2.0 TDI diesel can also suffer from high oil consumption and with this unit, we've also heard of DPF clogging, EGR valve malfunctions, turbocharger failures and timing belt wear. Few C8 A6s will have air suspension apart from the rare allroad version, but if the one you're looking at does, check the system thoroughly when you test the car and make sure it rises and falls through its various modes as it should. The most reported C8-era A6 faults relate to interior trim and non-engine electricals. We've had some reports of issues with wear to the side bolsters of the leather seats, as well as squeaking front brake pads, so it's worth looking out for both of those. There were a few issues with the car's infotainment system, with phones not connecting properly and flickering screens being the main problem. The DSG automatic gearbox should be checked to make sure it's had a regular oil and filter change, as should the quattro four-wheel-drive system (if fitted). Many A6 models will have been company or lease cars and, as a result, you should check the condition of the bodywork carefully. The high-quality fit and finish of an A6 also makes it an ideal candidate for clocking, so ensure the history is absolutely verified. If the A6 you're looking at has a panoramic glass roof and was an early C8-era model, be aware that on a few cars, this roof became unstuck from its frame.

Replacement Parts

(approx based on an A6 45 TDI (2019) - Ex Vat) An air filter costs in the £84 bracket. An oil filter costs around £6. A fuel filter is around £27. Front brake pads sit in the £58 to £91 bracket for a set; for a rear set, it's around £25. Front brake discs sit in the £51 bracket; for a rear pair, you're looking at around £77-£186. A headlamp is in the £968-£1,170 bracket; and a wiper blade is in the £11-£19 bracket.

On the Road

Previous A6 models never particularly prioritised a dynamic driving experience but this one offered a decent step forward in that respect, despite the fact that entry-level four cylinder models continued to buck the class trend by pushing power through the front wheels. Dynamically, that's a limiting factor, but with this C8-series design, Audi's engineers worked around it by building in a stiffer MLB-Evo chassis, a more sharply-responding variable 'Progressive' steering rack and a very effective optional adaptive damping system. Arguably the most important changes made here though, took place beneath the bonnet. Various engines were on offer but the sales focus was on the two mainstream diesel powerplants this car was launched with. Both were fitted with Audi's latest MHEV mild hybrid technology. This uses a clever electrical system - a 12V set-up on four cylinder models and a 48V system on the V6s. The result was an improvement in torque, power and throttle response but of course the technology was chiefly there to boost efficiency - at cruising speeds (where the car can coast with the engine switched off) and in traffic (where the MHEV set-up gives extended stop-start intervals). An improved version of Audi's quattro 4WD system was optional on the popular 40 TDI diesel variant, but quattro was standard for those who could stretch to one of the V6 models - the primary one is the 286PS 50 TDI diesel, but there's also a 340PS 50 TFSI petrol derivative. At the V6 level in the range, original customers could have the option of pillowy air suspension and a 'Dynamic all-wheel steering' package which delivered greater cornering agility and parking manoeuvrability. With the A6 50 TFSI e PHEV, the drivetrain was based around the brand's usual four cylinder 2.0 TFSI petrol engine, to which was added an electric motor integrated into the auto gearbox. That motor was originally powered by a 14.1kWh lithium-ion battery pack which, when fully charged, could allow the car to run in all-electric motion for up to 34 miles (WLTP-rated). Later in C8 production, Audi provided this PHEV variant with a larger battery offering greater EV range. For the original 50 TFSI e, there was a total system output of 299PS and 62mph from rest takes just 5.5s. In all-electric mode, the car can cruise at up to 84mph - or up to 152mph with the engine in use. The top RS 6 Avant used a 40 TFSI petrol V8 with 600PS. Whatever your engine and driving set-up choice in this C8 design, highway cruising in this A6 is impressively silent. And it's for this kind of driving that Audi offered the option of building in a package of so-called 'Level 3' autonomous driving tech. The 'Traffic Jam Pilot' system original buyers could specify on this car only allowed that facility on properly divided major roads at speeds of under 37mph but in operation, it was undeniably impressive. As were the associated 'Parking Pilot' and 'Garage Pilot' systems that allowed A6 owners to remotely park their cars when they reached your destination.

Overall

Did Audi do enough with the C8-series eighth generation version of this A6? Many thousands of managers who between 2018 and 2025 put thousands of miles under the wheels of their new A6s seemed to think so. As with previous designs in this model line, they valued this one for its quiet, understated professionalism, further marvelling in this guise at its sophisticated technology and highly advanced cabin. Yes, there are probably more characterful cars in the class from this period than this smart, efficient and perfectly mannered business conveyance. But there's no doubt that in this form, it was a very complete and cost-effective choice in this sector. If this A6's blend of cool design, cutting-edge technology and peerless build quality sway you over a supremely relaxing Mercedes E-Class or a slightly sharper-handling BMW 5 Series from this period, no one could accuse you of making the wrong choice in this segment. Yes, to really like it, you've still got to really like Audis, but if you do, you'll find it easy to bond with this one. Some may still see this A6 as being a little remote compared to a status-conscious Mercedes or a proudly opulent BMW. For others though, that'll simply be part of this car's vorsprung durch tecknik appeal, its design full of intelligent technologies created to make your life easier and save you time. Is that all that really matters? At the end of the kind of very long day this A6 has been designed for, you might well think so.