The S4’s 3.0-litre V6 bi-turbo diesel might sound like it’s out of touch with the world today, but makes use of sophisticated technology to keep it green and clean. Much of this hinges on a 48-volt electrical system that powers an electric compressor (basically a turbocharger driven by an electric motor) that works with a regular turbocharger to make 345bhp and 516lb ft of shove.
And because the latter is available from just 1,500rpm the S4 isn’t just faster than a Jaguar XE P300 or Alfa Romeo Giulia Veloce in a straight line – the 0-62mph sprint is over in 4.8 sec – it’s also more flexible. In fact, it’s even more effortless to drive than the Mercedes-AMG C43.
Or it certainly would be if it wasn’t for Audi’s incredibly laggy and unresponsive automatic gearbox. The noticeable delay when you put your foot down frustrates when diving for traffic gaps on a roundabout; the S4 lurches forward with a sharp jolt when the power does kick in. Thankfully this hesitance can be reduced by knocking the gearbox into its ‘Sport’ setting, or by using the steering wheel-mounted paddles for much smoother transitions between gears.
If you’re worried that a diesel won’t sound a patch on the petrol six-cylinder engine in the C43, don’t be so hasty. Thanks to an electronic sound-generator (read: fake exhaust sound) it sounds more like a petrol V8, but without seeming too contrived like some similar systems can. Indeed, its exhaust note is way meatier than the four-cylinder engines of the XE and Giulia can offer, and is easy to appreciate thanks to how well the S4 suppresses wind and and road noise.
Like the XE and the C43, all that grunt is managed assuringly by standard-fit four-wheel drive. As a result, the S4 feels just as quick and stable during day-to-day driving, whether the road is wet or dry. It’s so well balanced you find yourself maintaining around corners without any effort, and the steering is nicely weighted to inspire confidence. It’s not the best handling car in the class; both the XE and the Giulia Veloce steer even more sweetly, the Giulia giving keen drivers an edgier dose of rear-wheel drive excitement.
As standard you get passive suspension but we’ve only sampled S4s with Audi’s adaptive setup. This comes with different driving modes that relax or stiffen up the car as required, but, in its softest Comfort setting, the ride is composed on the motorway and supple enough around town.