OM626

From autumn 2014 the entry-level diesel W205s — C 180 BlueTEC and C 200 BlueTEC, later C 180 d and C 200 d — ran a 1.6 taken from Renault's R9M, assembled in France and completed at Bremen. Unlike the Renault installations and the transverse OM622 in the Vito, this one was turned lengthways to drive the rear wheels, at 85 kW and 100 kW. The technology was genuinely current: steel pistons from Mahle in place of aluminum, a variable-geometry turbo whose turbine wheel is smaller than its compressor, cooled low-pressure exhaust recirculation drawn from behind the particulate filter, injection to 1,600 bar and SCR after-treatment.

The low 15.4:1 compression ratio is the signature of the R9M's friction-first design philosophy, and on paper the results were exactly what the CO2 rules demanded of a car in that class. On the forecourt it was a harder sell — a Renault-derived engine in the middle of Stuttgart's core saloon range is the kind of detail buyers notice — and it lasted only until 2018, when Mercedes' own modular OM654 arrived in 1.6-liter form and took the job back in-house.