2021 (21) Audi A6 40 TDI Black Edition 5dr S Tronic

By Jonathan Crouch

Introduction

Audi's much improved fifth generation A6 Avant was a large, luxurious estate that combined practicality with panache. In this C8-series form, which sold between 2018 and 2025, it was even higher-tech, better finished and cleverer than before and aimed to offer buyers a little more charisma and driving reward than the previous version could have. You can see why so many buyers in this segment like it.

History

In new car sales, Audi may not be too far ahead of its arch-rival BMW in terms of overall sales but in one segment at least, the Ingolstadt maker has long comprehensively beaten its closest rival: that of large, luxurious Executive-class estates. Their A6 Avant traditionally out-sells the rival BMW 5 Series Touring nearly two-to-one, so hopes were high for what the marque might achieve with a car that was smarter, safer and clever. Like this one, the fifth generation C8-era A6 Avant. This wasn't the biggest model in its segment but for many buyers, it offered the most complete all-round proposition in terms of model choice, practicality and technology, which explained why the other German brands took this contender so seriously. It was claimed to be the most complete large load carrier Audi had ever made. In 2019, the A6 Avant 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 2021. 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 Avant 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. This became 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. Inside up front, the cabin is as well appointed as you'd expect from a range-topping A6 model, with leather-and-alcantara-combination upholstery and impeccable fit and finish, plus most buyers will want the Audi Virtual Cockpit instrument binnacle digital display (standardised on later models). Media features are taken care of by the usual black panel MMI twin-screen system on the centre stack that features in all large Audis from this era, with a 10.1-inch screen for infotainment functions up top and a smaller 8.6-inch display (mainly for climate features) just below. Thanks to this car's long 2.93-metre wheelbase, the back seat offers reasonable space for three adults, but much more comfortable room for two and you get a fold down centre armrest with storage and cup holders. Out back in this estate model there's a 565-litre boot. The centre part of the 40:20:40-split rear bench can be retracted if you need to push longer items like skis into the passenger compartment without disturbing a couple of rear-seated folk. If you want to push the seat backs down completely, you do it by pulling on the cargo sidewall levers, which reveals a 1,680-litre space.

What to Look For

Not too much goes wrong with a C8-era A6 Avant. 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 Avant 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 Avant models never particularly prioritised a dynamic driving experience but this one offered a decent step forward in that respect, despite the fact that the entry-level four cylinder diesel model continued to buck the class trend by pushing power through its front wheels. Dynamically, that was a limiting factor, but with this 'C8'-series model, 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. Audi offered this A6 Avant with a wide range of engines, mostly with the brand's mild hybrid tech. The range kicked off with a couple of 2.0-litre four cylinder models, the first of them being the 40 TDI diesel (with 204PS). From that point on in the range, all A6 derivatives got quattro 4WD, starting with the other four cylinder model, the petrol-powered 45 TFSI quattro (which offers 245PS). Next up were a couple of 3.0-litre six cylinder models, the 50 TDI quattro diesel (286PS) and the 55 TFSI quattro petrol (340PS). Those wanting an SUV alternative were offered the allroad A6 Avant model with its air suspension and raised ride height. The allroad quattro model offered buyers three engine choices; a slightly de-tuned 231PS version of the six cylinder 3.0-litre TDI diesel unit, badged '45 TDI'. And the two aforementioned six cylinder units, the 50 TDI and the 55 TFSI. At the top of the range sat two bespoke sporting models. The S6 quattro used the 3.0-litre six cylinder TDI diesel engine in an uprated 350PS state of tune. And the top RS 6 quattro had a 4.0-litre TFSI twin turbo V8 with 600PS, the result being 600PS, 0-62mph in 3.6 seconds, 124mph in 12 seconds and one queasy looking Labrador. As before, all A6 models were exclusively equipped with automatic transmission - a seven-speed S tronic gearbox, unless you opt for a 3.0-litre six cylinder diesel or the RS 6 (in which case the transmission will be an 8-speed tiptronic set-up to handle the extra torque). 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

This, even BMW and Mercedes would reluctantly have to admit, is a beautiful piece of engineering. It always has been. The A6 Avant was, after all, the first cars in its class to offer things like bonded-in flush glazing, a galvanised bodyshell, V6 TDI power, four wheel drive and advanced twin-clutch automatic gearboxes. And in this improved smart-suited fifth generation C8-series guise, the cleverness continued, an extra dose of visual charisma blended with high technology and premium quality unsurpassed in this sector. This car's drawbacks, such as they are, don't appear to bother many potential buyers. No it's still not the most spacious large executive estate in its class from the 2018-2025 era - but it's large enough for that not to matter. And it's true that the handling isn't especially aimed at driving enthusiasts, though original buyers could go a long way towards sharpening it by ticking the right options boxes. This then, was a very complete product. A thorough case, if ever there was one, of vorsprung durch technic.