From 2019 to 2024, the facelifted `S4 B9` takes on a noticeably different role in Europe, leaning far more toward fast long-distance cruising than showy sports-saloon theatrics. Against a BMW 3 Series, it sells itself through a `V6 TDI`, strong pulling power, `quattro` traction and a very high comfort level. As a used buy it can feel reassuring because it does everything well, but its engineering is far denser than that of an ordinary well-optioned diesel saloon.
The core issue is the `3.0 TDI V6` `EA897 evo` with `48 V` mild-hybrid hardware, especially under codes such as `DEWB` or `DMKC` depending on year and market. Engine, `EGR`/`DPF`/`AdBlue` after-treatment, the `48 V` circuit, the `12 V` battery, cooling, the `tiptronic` gearbox and software history all have to be read together. A car that feels fine for a few minutes can still hide unclear regeneration behaviour, weak `48 V` management or servicing that has been pushed back.