Diesel is dead, right? If so, why is Audi, the company whose VW parent did more than any other to imperil it, now replacing performance petrol ‘S’ models with diesels like this S4? Why, for that matter, are Mercedes-Benz diesel sales rising in Europe? But that’s for another story.

For the Audi, the reason would appear simple: it makes sense. A 3-litre diesel with a 48V mild hybrid system can provide a compact estate with what quite recently would have been regarded as supercar performance, while returning over 40mpg.

It’s a brilliant powertrain, far superior to any petrol Audi V6 (including those used by Porsche), not just in power delivery but, oddly enough, sound too. It has enormous torque, effortless response, a pleasant throaty thunder and a great relationship with the quick-witted, eight-speed gearbox.

If the car to which it was fitted was similarly snappy, Audi would have a winner on its hands. But the S4 follows in a long line of high-performance Audis that build anticipation brilliantly on the straights, only it dash it from your hands in the corners. Even at quite modest efforts, the steering has too little feel, the chassis too little enthusiasm for the job.

Put it this way, if Audi had put as much attention into the steering and suspension as it did into honing the powertrain, I have no doubt that the S4 would lead the class.

Andrew Frankel

Audi S4 Avant

Price £48,000
Engine 3.0-litres, 6 cylinders, turbo
Power 342bhp
Weight 1785kg
Power to weight 192bhp per tonne
Transmission Eight-speed automatic, four-wheel drive
0-60mph 4.8sec
Top speed 155mph
Economy 40.9mpg
CO2 TBC
Verdict Should be superb; it isn’t

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