OM656

By the mid-2000s the in-line six had been retired from Mercedes-Benz passenger cars in favor of the compact V6, and the OM 642 held that ground for a decade. The OM 656 took it back. Introduced with the facelifted W222 S-Class in 2017, it shares its 90 mm cylinder spacing and roughly half-liter cylinder with the four-cylinder OM 654, which makes the two engines largely the same parts in different quantities: aluminum block, steel pistons, NANOSLIDE bores, stepped combustion bowls, two-stage turbocharging, and CAMTRONIC variable valve lift — a first on a Mercedes diesel.

In the S 350 d it made 286 PS; in the S 400 d, 340 PS and 700 N·m, which the company billed as the most powerful series-production car diesel it had ever offered, on around seven per cent less fuel than the V6 it displaced. From there it went everywhere the OM 642 had been and further — CLS 400 d, E 400 d, GLE and GLS, and the W463 G 400 d, a straight-six diesel in a body shape drawn in the 1970s. A 48-volt version arrived in 2023 with an integrated starter-generator worth another 15 kW and 750 N·m beneath it.