Mercedes-Benz C-Class C300d 2021 UK review

We all know it, and yet there is still something mildly grating about a C300d not having a creamy 3.0-litre engine.

In fairness, car manufacturers have by now figured out how to make an engine of just about any configuration feel as refined as it needs to, even though BMW still fits a straight-six diesel to the 330d. Instead, the most powerful diesel C-Class comes with a 261bhp twin-turbo 2.0-litre, assisted by a 48V mild-hybrid system.

With the whole C-Class range now being four-cylinder only, it’s almost as though what powers it is incidental, and features like the revamped MBUX multimedia system are of greater importance in a new model. Whatever the case might be, the traditional elements such as the engine and suspension behaviour still need to stack up.

This C300d was also our first opportunity to sample a right-hand-drive example of the new C-Class in near UK spec. Although our test car was still a mix of AMG Line Premium and AMG Line Premium Plus, it was representative in that all C300d's in the UK come as some variation of AMG Line, including its sports suspension and 18in or 19in wheels. And that’s not necessarily a good thing.

The natural order of things is that a BMW 3 Series is firm but engaging to drive, while a C-Class trades some sharpness for ultimate refinement. The reality is that the big wheels crash through surface imperfections and that the body never quite settles down over a bumpy road, either, reactively following the surface rather than smoothing it out for its occupants.

On previous generations, air suspension was an option, but UK cars now all come on the confusingly named ‘Selective Damping System’. They are not adaptive dampers with different selectable settings, but passive dampers that supposedly react differently to high- and low-frequency inputs. Actual adaptive dampers are offered in other countries, so Mercedes UK should really reconsider, because the C-Class needs them. 

The C-Class steers pleasingly enough, with reassuring heft, precision and turn-in, but if you want a driver’s car, there are still better choices available, because it’s a little too stodgy to call it fun.

At least Mercedes hasn’t forgotten how to make engines and gearboxes. With 261bhp and 406lb ft, it’s more than brisk enough in all situations. It has a fairly typical refined four-cylinder diesel sound, although if we’re nitpicking, there are quieter units around. It works seamlessly with both the nine-speed automatic and the mild-hybrid system, which lets the engine shut down when coasting to a stop.