OM607

The OM607 is the Renault K9K, the 1.5-liter dCi that entered production in 2001 and had passed ten million units by 2013, which makes it one of the most-built diesel engines of its generation. Mercedes-Benz took it on under the alliance agreed with Renault-Nissan in 2010. It came first in the Citan van of 2012 — itself a rebodied Renault Kangoo, assembled next to the Kangoo on the same line at Renault's Maubeuge plant in northern France — and then in the entry-level A-, B-, CLA- and GLA-Class diesels.

What Stuttgart altered was calibration and ancillaries rather than architecture. Underneath sit an iron block, an aluminum head, a single belt-driven camshaft, two valves per cylinder and common-rail injection, offered as 75, 90 and 110 PS in the Citan 108, 109 and 111 CDI. Set against a company that had spent forty years defining what a Mercedes diesel was, buying one in was an admission that the smallest cars in the range could no longer carry the cost of a bespoke engine of their own.