OM648

The largest of the three engines Mercedes launched in 2002 on one shared architecture, it took over from the OM613 with the family's common 88 × 88.3 mm cylinder, cast-iron block, aluminum head, chain-driven twin camshafts and four valves apiece. Common-rail injection at 1,600 bar and a variable-nozzle turbocharger produced 204 PS at 4,200 rpm and 500 N·m held from 1,800 to 2,600 — enough, Mercedes claimed, to take a W211 E 320 CDI to 60 mph in 6.6 seconds while returning motorway economy no petrol six of the size could touch.

The applications were few and grand: the E 320 CDI, the W220 S 320 CDI, and from 2005 a de-rated 177-PS E 280 CDI below them. Then it was done. None of the OM646 EVO work reached the six, because from the summer of 2005 the new OM642 V6 began replacing both it and the five-cylinder OM647, packaging better and costing less to build in volume. Mercedes has since gone back to the straight six with the OM656, but the OM648 closed out the older line.