The wider Audi A4 range has had a fairly major overhaul as part of the mid-cycle facelift with which this S4 TDI arrives, with 12V mild-hybrid powertrain technology being applied across most engines and a pair of new lower-end diesel options being added to bolster the car’s appeal as a big-selling company car.
You can’t imagine the range-topping S4 TDI will be a hugely popular fleet option, diesel or otherwise, but then there’s plenty here to entice private buyers. Now the only A4 available in the UK with more than four cylinders, the S4 adopts a 2967cc V6 that’s notably different from Audi’s old BiTDI, which powered the last SQ5 TDI.
With one conventional exhaust-driven turbocharger and one electrically actuated compressor, plus a new 48V electrical architecture with an enlarged starter/generator motor driven by current from a lithium ion battery, the engine produces 342bhp at the tip of a fairly peaky-looking power curve.
Thankfully, the 516lb ft of torque the same engine makes, between 2500rpm and 3100rpm, ought to result in a decidedly unpeaky-feeling power delivery overall.
The new S4’s electrical system and starter/generator mean the hybrid powertrain can regenerate power at an impressive rate, too – at up to 8kW – which contributes to lab-tested WLTP combined fuel economy of up to 40.9mpg, depending on optional specification. Addressing the veracity of that claim will be as important as any performance indicator for this test – and we’ll get to that.