Audi S4 saloon review

The Audi S4 is a high-performance variant of the Audi A4 saloon, which commands a premium of around £18,000 over the cheapest model in the A4 range. For that, you’ll get a turbocharged 3.0-litre diesel engine which produces 336bhp, Audi’s quattro four-wheel drive system, plenty of equipment as standard, and some styling tweaks. The S4 Avant is the estate version of the S4 which costs a further £1,400 or so. 

Rivals of the Audi S4 include higher-powered versions of the BMW 3 Series, and the Mercedes-AMG C-Class C43. These both cost around the same price but use petrol engines instead of diesel. The S4 is by no means the highest performance version of the A4 – for even more power there’s the twin-turbocharged 2.9-litre petrol-powered Audi RS4 which takes things up a notch further. 

While it’s no less potent than its petrol-powered rivals, the diesel S4 has a distinctive feel to it, and is fitted with an innovative electric compressor to help the engine feel powerful from low revs. It leaps forward keenly when you put your foot down and can overtake slower traffic with ease. It’s capable of 0-62mph in 4.6 seconds and has an electronically limited top speed of 155mph while still returning just under 40mpg.

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The S4 was facelifted in 2019 which mostly just sharpened up the car’s appearance. Its plush interior remained mostly the same apart from updates to the Audi infotainment system and improved graphics for the Virtual Cockpit digital instrument cluster.

The latest Audi A4 is one of the most economy-focused performance saloons on sale, with loads of technology designed to save fuel as well as boost performance. An advanced diesel engine is bolstered by Audi's 48-volt mild-hybrid system, allowing engine-off coasting and longer periods of stop-start in traffic.

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Official figures stand at 39.8mpg and 185g/km of CO2 emissions, so drivers will be able to take long trips without having to worry about frequent fill-ups. The efficiency figures also make the diesel S4 quite a bit more economical than petrol rivals like the Mercedes-AMG C43 4MATIC, which can manage up to 29.4mpg (213g/km).

The S4 sits in the top company-car tax band and costs £165 a year in VED car tax, but with a luxury car surcharge of £355 in the first five renewal years because it costs more than £40,000 to buy.

The S4 we drove recently left us in no doubt Audi has made a genuinely rapid and capable car. Its adjustable suspension can be configured to iron out potholes effectively or provide extra stiffness for an involving drive, while the conventional eight-speed automatic gearbox is arguably smoother than Audi’s dual-clutch S tronic set-up, even if it’s not quite as quick to change gear. Using the steering wheel shift paddles for the gearbox provokes a pleasing blip from the engine when shifting down a gear, while changes in auto mode are seamless.

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The 3.0-litre six-cylinder diesel engine uses turbocharging and an electric compressor at low revs to help produce its 336bhp. It’s responsive for a diesel and the S4 accelerates rapidly enough to pin you to the back of the seat with some force. The car surges forwards when you press the accelerator, and even makes a satisfying deep bellowing noise, getting from 0-62mph in 4.6 seconds.

The S4’s steering leaves a little to be desired. It’s accurate enough and to make it easy to place the car on the road, but we wish there were a little more feel through the steering wheel, as the lack of feedback makes it tricky to gauge how much grip the front wheels have and how slippery the road is. In truth, this is only a problem that presents itself on winding B-roads, but the fact remains that if driver involvement is a top priority, BMW’s 3 Series is the better car.

Audi enjoys an enviable reputation when it comes to interior design, and getting into the S4 leaves you in no doubt this is justified. The quality of materials on show is impressive, while the overall design is ergonomically sound and aesthetically pleasing, though it’s a shame the infotainment screen is now fixed in place on top of the dash, as it's a more cluttered design than the retracting screen found in the previous-generation model.

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All S4s get incredibly comfortable, supportive Nappa leather seats, which are heated and have a massaging function in the front. Rear seat passengers get their own controls for the air-conditioning, and the adjustable suspension can be configured to provide a cosseting and comfortable experience over poor road surfaces.

Every version of the S4 has 19-inch alloy wheels, LED headlights, LED rear lights and dynamic rear indicators. A rear-view camera is also standard, together with Audi’s parking system plus. Interior technology includes sat nav, Apple CarPlay and Android Auto, Audi’s Virtual Cockpit digital instrument cluster and wireless smartphone charging.

Upgrading to the S4 Black Edition adds black exterior trim, while the top Vorsprung version brings a sport differential for the quattro four-wheel drive system to improve agility, a tilt and slide sunroof, head-up display and a Bang & Olufsen premium stereo system.

The whole point of high-performance models like the Audi S4 is that they offer the practicality of the car on which they’re based, together with serious speed. As such, the S4 is just as practical as the A4 saloon.

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There’s plenty of space for adult passengers in the rear, while the 480-litre boot is identical in size to the BMW 3 Series’. Choose the Avant model and you get a more practical estate boot which can hold 505 litres.

As a niche model, the S4 lies outside the remit of Euro NCAP’s safety tests but it doesn’t really need its own assessment because the standard A4 saloon has already been checked. This scored the full five stars, with excellent scores for adult and child protection (90% and 87% respectively).

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All S4s come with an ‘active’ bonnet that rises to shield pedestrians from the hard engine components lying beneath, plus an autonomous emergency braking system that’s effective at urban speeds. Mandatory systems such as ISOFIX child seat mounts and electronic stability control are all present and correct, as you would expect.

The standard Audi A4 was rated poorly for reliability in our 2022 Driver Power owner satisfaction survey of cars currently on sale in the UK. Curiously, despite around 16% of owners reporting an issue in the first year of ownership, it came in 70th place in the reliability leaderboards out of 75 cars. As a brand, Audi came in 22nd place out of 29, coming in behind many rival manufacturers. Around 20% of all Audi owners reporting issues with their cars in the first year, reliability was average.