OM651

The brief written in 2005 was unusually specific: one four-cylinder diesel that could be installed both longitudinally and transversely, share as much hardware as possible across every output, and meet Euro 5 at its 2008 launch with the headroom to reach Euro 6. What emerged was a cast-iron block under an aluminum head, twin camshafts driven by a mixture of chain and gears, balance shafts, piezo injectors on common rail, and either a single variable-geometry turbo or a two-stage BorgWarner pair in which a small high-pressure unit hands over to a larger one. Two strokes gave 1.8 and 2.1 liters, 95 to 204 PS.

By 2013 Daimler's own engineers were describing it in the language of a platform: twenty vehicle categories, 760,000 engines a year, eighteen hardware variants covering 1,014 functional versions for emissions rules from Euro 1 to US BIN 5. It ran in A-Class hatchbacks and 3.5-tonne Sprinters, in the GLK that took the diesel back to America, and — under the Renault-Nissan agreement — in the Infiniti Q50 2.2d, which used the C 220 CDI's 125 kW and 400 N·m untouched. Timing-chain wear and early injector failures shadowed its reputation. The OM654 began replacing it in 2016.