Audi’s mid-table S performance range continues to turn in a diesel direction, with the debut of the S5 TDI

First it was the SQ5, then the new S6 and S7, and now Audi’s fitted its new mild-hybrid V6 turbo diesel in its smallest application yet, the S5. The move heralds a return of the S5 after a brief hiatus due to WLTP emissions regulations, but this time with the brawny diesel in lieu of the previous 3-litre turbo petrol.

As in its other applications, the S5 TDI features a 48v mild-hybrid system that feeds both a small electric compressor and belt-driven starter motor/generator. These electrified powertrain components are then connected to a single-turbo 3-litre V6 diesel engine, together producing 255kW, with a peak torque figure of 700Nm available between 2500rpm and 3100rpm. Although power is down 7kW, torque grows by a substantial 200Nm (around the same as a 2.0 Mazda MX-5, no less) over the old petrol model.

> Click here for more on the Audi S6 and S7 TDI

As a result, the new S5 TDI will reach 100kmh in 4.8sec (the heavier Sportback manages 4.9sec), only 0.1sec slower than the previous petrol-powered S5. It will then run on to a 250kmh limited top speed. These remarkably similar performance figures also come with an estimated 20 per cent reduction in fuel consumption.

The diesel engine is connected to an eight-speed torque converter automatic transmission and the requisite quattro all-wheel drive system. Audi’s torque-vectoring Sport Differential is on the options list, as are magnetorheological adaptive dampers and these are controlled via a new electronic chassis platform management system that coordinates all the active chassis components via one central electronic brain.

The S5 is otherwise unchanged, Audi taking the decision not to hold the new TDI powertrain back until the A5’s upcoming mid-life refresh.