Used Audi S4 (B9, 2016 - 2024) – review, prices and specs of a punchy M340i alternative

Understated almost to the point of anonymity, the S4 is the mid-level performance version of the Audi A4 saloon that’s seen more heart transplants than Addenbrooke’s Hospital. It’s swapped between twin-turbocharged and supercharged V6 engines over the years and once even had a howling V8. For its final outing in B9 form, the S4 had both turbocharged petrol V6 and yes, diesel engines. Combined with an eight-speed automatic transmission and the ubiquitous quattro all-wheel drive, the B9 S4 was a brutally effective device in all forms.

With the A4 put out to pasture, that means the S4 (and indeed RS4) go the same way, with the new petrol-only mild hybrid Audi S5 taking its place as Audi’s warmed-over small saloon. It’s here to fend off both the Mercedes-AMG C43, and the most potent non-M version of BMW’s 3-series, the M340i.

The petrol S4’s combination of a smooth, punchy powertrain, svelte styling and exceptional build quality made it a desirable mid-level performance saloon. The S4 TDI, while not a heady, evocative top-end machine, has brutally effective barrel-chested mid-range performance.

Audi S4 – Engines, performance and 0-62 time

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Over three generations and just under 15 years, the Audi S4 went from a V8, to a supercharged V6, to a turbocharged petrol V6, to a diesel V6. We can’t think of a model line that chopped and changed so much over such a short space of time.

It might have lacked the exotic flare of a naturally aspirated V8, and the instant punch of the previous B8 S4’s supercharged V6, but the turbo mill here found a more artful balance between brisk performance and not being able to achieve more than 30mpg on any given day. The diesel V6 was even more of a correction, putting 40mpg to within the grasp of Audi semi-supersaloon drivers.

> Buy a used Audi S4 saloon

In the petrol B9 S4, launched in 2016, the single-turbo petrol V6 was good for 349bhp at 5400 to 6400rpm and 369lb ft from 1370 to 4500rpm. Performance was about where one might expect, with both the saloon and estate slipping under the 5.0sec to 62mph barrier (4.7 and 4.9sec respectively). Top speed was a limited 155mph.

Audi didn’t hold anything back with the updated S4’s 3-litre V6 TDI engine compared to its larger siblings. It developed the same 344bhp at 3850rpm, and no less torque, with a massive 516lb ft available between 2500 and 3100rpm.

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Aside from the diesel engine, the B9.5 S4 also gained a 48-volt electrical system, mild-hybrid technology, and an electric compressor to supplement the conventional turbocharger. The hybrid tech used a belt-driven starter-alternator to allow for start-stop functionality and engine-off coasting, while the electric compressor was said to improve throttle response.

As with the S6 and S7, Audi’s quoted fuel economy figures showed only a small improvement over the petrol predecessor, but they’re also comparing apples with oranges. The 40.9mpg combined (39.8mpg for the Avant) was novel at the time for being recorded on the tougher and more realistic WLTP test.

> Buy a used Audi S4 Avant

In saloon form the diesel S4 was capable of 0-62mph in 4.8sec – two-tenths quicker than an S6 Avant and just a tenth shy of the petrol S4, despite a small horsepower deficit – while the diesel S4 Avant was a tenth slower than the saloon. Both reached an electronically limited 155mph.

It must be said, there's an unexpected character to the sound of the diesel V6, and it’s hard to fault how effective it is. Below around 2000rpm, the engine isn’t overly enthusiastic, most easily discovered if you’re changing gear manually rather than leaving the ’box in auto. Proper electric torque-fill rather than half-hearted energy recuperation would be welcome here – see the 2025 Audi S5 again.  

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Power in both cases was sent through an eight-speed Tiptronic automatic transmission and quattro all-wheel-drive system with self-locking centre diff, while the option of a locking ‘Sport Differential’ at the rear was also available. The eight-speed ’box itself can be frustratingly slow to wake up compared to a DSG. If you’re pulling onto a roundabout or out of a junction, you might find yourself sprinting off at full chat because you’ve sunk the pedal trying to get some kind of response.

But avoid the low-speed torpidity and ignore the last thousand rpm or so before the red line, and the diesel S4 has real wallop. Overtaking is done in a flash and throttle response is impressive in that mid-range band, with an offbeat growl to the exhaust note.

As with the larger S6 and S7, the diesel unit also makes the S4 a fantastic cruiser, settling down to near-silence but always a quick downchange or two away from sprinting up to autobahn speeds. Top gear is tall enough that it’s overly keen to change down on motorway inclines, but whether you use the paddles or leave the transmission to its own devices, changes are always smooth and swift.

Audi S4 technical highlights

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Aside from the switch from supercharging to turbocharging technology, the B9 S4 also adopted an eight-speed automatic gearbox instead of the previous car’s dual-clutch S-tronic transmission. The first B9 S4 and S4 Avant were also around 75kg less than the B8 S4s too, at 1630kg and 1675kg respectively. The MHEV diesels gained a good bit of weight, at over 1800kg. The S4 was, of course, underpinned by a four-wheel-drive chassis. Under normal circumstances power is split 40/60 front to rear, but up to 70 per cent of power can go to the front axle or 85 per cent to the rear should conditions demand it. 

The active torque vectoring ‘sport differential’ for the rear axle worked with the B9 S4’s torque vectoring by braking system which lightly brakes the inside wheels during hard cornering to create a more agile feeling. Also on the options list was Continuous Damper Control, which featured Comfort, Auto and Dynamic settings, and the variable-ratio Dynamic Steering system.

The updated 2020 diesel S4, along with the rest of the A4 range, adopted a 10.1-inch central touchscreen standing proud of the dashboard, with updates to the MMI interface and infotainment functions. It didn’t quite have the flash of Audi’s larger models of the time, but the screen was at least fairly intuitive, if distracting. A shame, though, that the rotary UX controller was ditched for the facelift.

The interior design arguably didn’t need much changing, and has done so less than the exterior, which LED headlights and tail lights aside, isn’t an entirely successful update to our eyes – the fake plastic ur-Quattro-aping trim above the grille and token blistered arches appear rather fussy.

Audi S4 Ride and handling

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The first thing that strikes you when you drive a B9 S4 is how refined it is. Even on the 19-inch wheels, with the Continuous Damper Control and the clever Sport Differential, it rides beautifully in Comfort mode. On smooth-surfaced test routes, even Dynamic mode did little to ruffle the fluid composure of the car. Allied to the almost invisible eight-speed automatic and instantly responsive, gutsy engines, B9 S4s make effortless progress.

The dynamic steering system was improved for the B9 S4 too but there’s still an initial jumpiness that feels slightly odd and it’s so light that you don’t feel there’s a real connection to the front wheels. With a few minutes to adapt, the rate of response feels much more natural and consistent than those hateful early systems.

The chassis is partly brilliant and partly disappointing. The ride really is fluid and allows you to build up a nice, easy rhythm, and while there’s quite a bit of body roll the car has a sense of effortless control that seems to fit with its easy-going but impressive turn of speed. 

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The balance is also pretty good. Of course, it can be made to understeer if you don’t listen to the howling tyres but if you turn the car in slightly slower and then commit to the throttle you feel the sport diff sending power to the outside rear tyre. As the corner unfolds a small yaw angle builds and then stabilises, so you exit each corner with the car driving forwards but held in a shallow oversteering angle.

The S4 feels slightly too soft-edged, perhaps befitting its remit as the stepping stone model to the RS4. The chassis is clearly very well sorted, the balance with the sport diff is adjustable and not relentlessly understeery, but the weight savings advertised don’t really make themselves felt. Instead of feeling lithe and agile the S4 too often feels like you’re coercing it into revealing its sportier side. 

It’s not like it should be crashy and edgy, but a small increase in body control and turn-in response, a bit more volume for the exhaust and sharper gearshifts would transform the car. Indeed, the 2025 Audi S5 moves the game on in this sense. The B9 S4 too often feels just like a ‘normal’ A4 that just happens to have a load more performance, rather than a true performance derivative. It should be said that the S4 saloon is tangibly more agile than the Avant model and feels slightly keener to entertain.

Price, rivals and successor

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The petrol B9 S4 was taken off-sale during the sweeping WLTP reforms of 2018 and 2019. Rather than go through the motions of re-certifying a new petrol version before the A4’s range-wide update, Audi left it off-sale until the high-performance V6 diesel engine arrived.

The market for warm saloons with potent six-cylinder engines has been oddly resilient over the last ten years. Both Mercedes and BMW met Audi with responses at every turn. The C43 was no halfway-house performance car on the road, with an impressive combination of outright punch and theatre from its 3-litre turbocharged V6 engine. It drove well too, its sonorous petrol engine and a slightly less aloof feel to its controls making the Mercedes-AMG C43 probably the more fun of the pair.

The B9 S4 suffered with unfortunate timing, the G20 BMW M340i arriving just in time to head off the facelifted model. Powered with a 376bhp 3-litre turbocharged in-line six, it’s difficult to recommend either the Merc or the Audi in its place. The S4’s trump card in its second B9 iteration was clearly economy, going over a third further on every gallon of fuel and costing you less to tax. That, plus the S4 diesel’s easily accessible performance, did win Audi a few more fans. Fans whose efficiency expectations may not be met by the 2025 S5 that takes over from the S4, even if

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Prices vary for the B9 Audi S4, given it had a good long innings with a variety of specifications. Earlier V6 cars are understandably a bit cheaper but the diesels with strong miles are still attainable. Expect to pay between £15k and £21k for a petrol and between £20k and £40k for the later diesel. Desirable options to look out for include the sports exhaust on the petrol, Continuous Damper Control suspension, the Sport differential and matrix LED lights.

Specs ranged from standard, all the way up through Black Edition to Vorsprung, the latter adding unique alloy wheels, the Audi Matrix LED headlights, standard fitment of the Sport differential, Bang & Olufsen audio and a head-up display.

Audi S4 (B9) specs