Audi A6 40 TDI S line (2023) review
Audi has updated the A6 to keep it on sale for a while longer. Does this diesel saloon still have relevance?
Neil Briscoe
Neil Briscoe

Published on January 23, 2024

Audi A6 range overview

To say that the Audi A6 is feeling a bit old seems odd when you dig into the diary and discover that this version of the long-serving executive saloon was only introduced in 2018. Of course, being a pre-pandemic launch, that makes it seem even longer ago, and that's exacerbated by the fact that its two biggest rivals - the BMW 5 Series and the Mercedes-Benz E-Class - have recently been launched as entirely new generations of car, with fully-electric options (in the shape of the standalone EQE for Mercedes).

That is also the future for the A6 of course. The all-electric A6 e-tron saloon and Avant estate should have been going on sale about now, but have been delayed by hold-ups developing the complex software needed for such powerful (600hp+ at the top end) and long-ranged (600km+) cars (as have the closely related Audi Q6 e-tron and Porsche Macan - all three cars use the same 'Premium Platform Electric' underpinnings).

The plan was always to keep the petrol, diesel, and hybrid-engined A6s in production and on sale for a while alongside their new all-electric brother, it's just that the 'C8' A6 (that is its internal Audi model code) is having to go it alone a little longer.

So, Audi has given the A6 a light refresh to try and keep it in the hunt against its competition from Stuttgart and Munich, adding an updated driver's instrument screen, a new reversing camera, freshened-up bumpers and grille, new alloy wheel options, and new colours including Ascari Blue and Grenadine Red.

There is, of course, the option of going partially electric in the current A6 line-up, with a choice of 50 TFSI e (with 299hp) and 55 TFSI e (with 367hp) quattro plug-in hybrid powertrains that promise an electric-only range of up to 68km. However, our test car is a little more old-school. Sure, it's a mild-hybrid and all, but this 40 TDI is powered by a diesel engine, using the 204hp version of the long-serving 2.0-litre TDI engine. Diesel might be waning in popularity overall in the market, but can it still provide some relevance installed in the handsome nose of this A6?

The Audi A6 model range

Audi has kept the A6 model line-up simple, and for the mainstream models there's a straightforward choice of SE or S line versions. SE prices start at €58,925 for the 40 TDI front-wheel-drive model, rising to €77,515 for the more powerful 286hp V6 50 TDI quattro. You can also have the 50 TFSI e quattro plug-in hybrid for €72,090 in SE spec. If you want to upgrade to an Avant estate in SE form, that'll be €64,680 for the 40 TDI, €86,510 for the V6 50 TDI quattro, or €74,095 for the 50 TFSI e quattro PHEV.

Standard SE equipment includes 18-inch alloy wheels, LED lights, electric folding and heated door mirrors, adjustable lumbar support for the front seats, leather upholstery, heated seats, ISOFIX child seat mounts for the outer two rear seats and the front passenger seat, two-zone climate control, aluminium dashboard trim, ambient lighting, the 'Virtual Cockpit' digital driver's display, a seven-inch touchscreen, smartphone connectivity, a three-year subscription to Audi Connect internet services, a reversing camera and parking sensors, cruise control with speed limiter, and child-proof rear locks with individual controls on the driver's door panel.

Sportier S line models start at €63,220 for the 40 TDI front-drive saloon, rising to €68,830 for the 40 TDI quattro, and €82,275 for the V6 50 TDI quattro. There's the 50 TFSI e plug-in hybrid in S line trim for €75,770 and if you want the Avant estate, that's going to be €68,155 for the 40 TDI, €74,340 for the 40 TDI quattro, €91,595 for the V6 50 TDI quattro, or €78,585 for the 50 TFSI e quattro.

S line equipment includes 19-inch alloy wheels, dynamic indicators, Matrix LED headlights, sportier bumpers and body kit, a headlight cleaning system, sports front seats, matte brushed aluminium trim, stainless steel pedals and sports suspension.

For the more powerful 55 TFSI e quattro plug-in hybrid, there's a specific Competition equipment level, which includes four-zone air conditioning, bigger brakes with red-painted calipers and sports suspension. Prices for the 55 TFSI e quattro Competition are €76,830 for the saloon or €79,645 for the Avant estate.

There are two further A6 models, both much more overtly sporty. For €105,665 as a saloon or €109,405 as an estate, you can have the V6 diesel-powered S6 with 344hp. The S6 comes with 20-inch alloy wheels, a body-coloured rear spoiler, four-zone climate control, keyless entry and ignition, and 'Valcona' leather upholstery.

Finally, there's the mighty 4.0-litre twin-turbo petrol V8-engined Audi RS 6, with its 600hp and 800Nm of torque. It'll set you back €183,415 and is only available in Avant estate form. Standard equipment includes 21-inch alloy wheels, a roof spoiler, unique RS styling, HD Matrix headlights, a Bang & Olufsen sound system, quattro four-wheel drive with a locking central differential, uprated suspension and brakes, and RS front bucket seats.

CO2 emissions for the A6 line-up start at just 24g/km for the 50 TFSI e, rising to 136g/km for the 40 TDI, 166g/km for the 50 TDI, 181g/km for the S6 and 276g/km for the RS 6.

In 2018, Euro NCAP gave the A6 a full five-star safety rating, with scores of 93 per cent for adult occupant protection, 85 per cent for child occupant protection, 81 per cent for vulnerable road users and 76 per cent for safety assistance.

The Audi A6 40 TDI interior

In so many ways, the A6's interior is an object lesson in how to create a comfortable, ergonomically sensible, beautifully crafted car cabin. That, though, is not to say that there aren't a couple of demerits with which to deal.

First off, though, it's such a pleasure to be sitting down low again. With the ever-onward march of the SUV, it's becoming a relative rarity to test drive a low-slung four-door saloon, and the A6's driver's seat can be lowered right down for a truly laid-back driving position. While many reckon that the high-up seat of an SUV makes them feel safer, personally I feel much more secure sitting down low, closer to the car's centre of gravity. The sports front seats of this S line model, with their extending seat bases, are exceptionally comfortable and supportive, but it's a bit of a disappointment in a car with a €70k+ price tag that they're not electrically adjustable in any way.

The flat-bottomed, three-spoke steering wheel feels terrific to hold, and the revised 'Virtual Cockpit' driver's instrument panel is clear and informative. Across, in the centre console, is the twin-screen layout for the infotainment and climate control setup. The lower screen takes care of the climate control, and the upper screen is where you'll find your navigation, phone projection and so on.

This is only a partially satisfactory system. The menu layout is reasonably simple (although it takes a few too many clicks and sub-menus to do simple things such as dim the screens at night) and at least the climate controls get their own dedicated screen, rather than being yet another sub-menu on the main screen, but the haptic feedback (which tries to mimic the sensation of pressing a physical button when you touch the screen) is an odd sensation, and one that I have never acclimated to.

Equally, sometimes the haptic feedback is triggered even when you haven't pressed hard enough or long enough to trigger the function you were looking for, so it becomes doubly confusing - not to mention distracting when driving. Once again, we're forced to plead for the return of physical buttons, although it should be noted that the A6 at least has a proper volume control knob. Equally, it's worth pointing out that the physical buttons on the steering wheel are often fiddly and tricky to use, so physical controls are not infallible.

On the centre console, you'll find the flat-topped gear selector (all A6 models come with automatic transmissions now, either the seven-speed 'S tronic' dual-clutch unit as fitted here, or the eight-speed 'Tiptronic' automatic fitted to 50 TDI, S6 and RS 6 models), two cupholders and the switches for the electronic parking brake and auto-hold functions. Behind these, there's a large, but shallow, storage area under the armrest, and that's backed up by well-sized door bins. There's a 12-volt power outlet in with the cupholders, and a pair of USB-C sockets under the armrest.

In the back, there's ample legroom and headroom, and a sense (even if the tape measure only just bears this out) that there's a touch more space than you'd find in the E-Class or 5 Series. The rear seat is also set slightly higher than those in the front, so despite the generously proportioned front seats, you can see out well all-round. The rear of the cabin feels a bit bare, though. There are useful seatback storage nets, but other than that all you get is some air vents and a 12-volt socket.

However, with all the piano-black and aluminium trim, the A6's cabin is a touch dark and hard-edged. The build quality, as you'd expect, is exemplary with nary a panel out of place, but the general feel of the cabin is not especially welcoming. It feels more technical than it does warm, in contrast to the cabin of the new BMW 5 Series.

The boot, at 530 litres, is competitive for this class, out-doing the BMW 5 Series by 40 litres, although it's slightly smaller than that of the E-Class. Of course, you could always upgrade to the Avant estate, with its 565-litre boot, and as ever we'd recommend you do so.

The Audi A6 40 TDI S line driving experience

The 40 TDI unit is a 2.0-litre turbodiesel with mild-hybrid assistance (only a 12-volt system, though - you have to upgrade to a V6 engine to get the 48-volt mild-hybrid system) is a long-serving engine, but it has excellent all-round performance. A 0-100km/h time of 8.1 seconds may not seem too hot, but with 400Nm and a reasonable 1,700kg kerb weight, the A6 40 TDI feels pleasingly muscular in most driving environments.

Better yet, it can be spectacularly economical. It's debatable how much the mild-hybrid system is contributing besides some improved stop-start performance around town but drive this big A6 gently and you'll easily better 5.5 litres per 100km. Sit in, having freshly-brimmed the tank, and you'll be greeted by a very reassuring 1,200km range-to-empty figure. Even without trying to drive especially economically, a solid week's motoring in this A6 barely scraped through half a 73-litre tank. So, while, yes, it's still burning old-school fossil fuels, this A6 40 TDI is doing so at an impressively slow rate. It helps, of course, that it's a low-slung saloon and not a chunky, hefty SUV. The drag coefficient is a mere 0.27, which makes this a very slippery car indeed, hence that impressive long-journey economy.

It's not perfect, of course. There is noticeable diesel-y grumbling at low speeds (which in fairness fades into the background once you're cruising) and even with the mild-hybrid system, there's a lengthy delay between you asking for pull-away power and the engine and gearbox responding. That can make busy roundabouts or junctions far more of a chore than they ought to be.

Is it any fun to drive? In some ways, yes. There is an unquestionable joy in driving a vehicle that's not needlessly tall nor heavy, and the A6 responds to a twisty road with a reasonable level of enthusiasm. It lacks the sharp steering and poised sensation of the BMW 5 Series, and it's not as refined as the new E-Class (too much tyre roar at motorway speeds) but the A6 does carve a nice middle ground between the two. The steering is too light for much in the way of proper driving fun, and the sportier S line suspension means that those big tyres do occasionally slap into an obstacle with a slightly flat-footed sensation, but in general the A6 is comfortable, relaxing and pleasing to drive. As a long-haul motorway express, it's hard to beat and you'll have reached your destination long before anyone driving an equivalent EV will manage.

Our verdict on the Audi A6 40 TDI

Is the A6 40 TDI a bit old-school? With a big, simple diesel engine it kind of is, yes, but this black-pump-special still has some lessons to teach more modern electric and hybrid rivals, not least in just how easy and relaxing it is on a long journey. The cabin could be a bit more welcoming, and the steering a bit sharper, but overall, the Audi A6 continues to prove that it's a high-quality piece of work, with excellent comfort and space inside and subtly handsome lines on the outside. Old schools can still turn out star pupils, you know...

What do the rest of the team think?

As Neil mentions, the A6 isn't a new car now; against the newer offerings from BMW and Mercedes, it is really starting to feel old. Nonetheless, diesel is still an excellent option, especially for those doing big weekly mileages, and distance is something the A6 laps up with ease. I don't think it's the nicest cabin to spend lots of time in, as its materials and colours leave it feeling somewhat joyless and cold, as competent as it is. Finally, Audi could be more generous with its standard equipment, especially considering this model's time in the market.

Dave Humphreys - Road Test Editor

Regardless of its age, the Audi A6 is a good-looking car, especially so in S line specification on large alloy wheels. Remarkably, the low-profile tyres don't destroy the ride-handling balance and this car mixes competence in the corners and at speed with comfort and composure on the motorway. Sure, smaller wheels would be more comfortable again, but the bigger rims don't ruin the car. As Neil mentions, the step off from a standstill is oddly tardy unless you're forceful with the accelerator pedal or you choose the S mode for the transmission, though elsewhere the diesel engine acquits itself well with a massive range on a tank of fuel if that's the kind of thing you need. Sure, the new E-Class and 5 Series have dated this car, but by any other measure it's still an accomplished executive saloon that buyers will find satisfying to own.

Shane O' Donoghue - Editor


Tech Specs

Model testedAudi A6 40 TDI S line
Irish pricing€76,845 as tested; A6 starts from €58,925
Powertraindiesel - turbocharged 2.0-litre four-cylinder engine with mild-hybrid assistance
Transmissionautomatic - seven-speed gearbox, front-wheel drive
Body stylefour-door, five-seat saloon
CO2 emissions135g/km
Irish motor tax€210 per year
Fuel consumption5.2-6.0 litres/100km (47.0-54.3mpg)
Top speed246km/h
0-100km/h7.9 seconds
Max power204hp at 3,800-4,200rpm
Max torque400Nm at 1,750-3,250rpm
Boot space530 litres all seats in use
Towing capacity750kg unbraked, 2,000kg braked
Rivals to the A6 40 TDI S line (2023)