OM699

Mercedes-Benz wanted a mid-size pickup without the expense of designing one, so the X-Class was developed with the Renault–Nissan–Mitsubishi alliance, built on the Nissan Navara's F-Alpha platform, and assembled by Nissan in Barcelona. The engine followed the same logic. The OM 699 is Renault's M9T reworked for Stuttgart: displacement taken out to 2,298 cc, compression dropped from 16.0:1 to 15.4:1, new cylinder head and pistons. Nissan sold the same unit as the YS23, and it also worked in the Master, the Navara and the Alaskan.

Two versions reached the X-Class. The X 220 d used a single variable-geometry turbo for 163 PS; the X 250 d was twin-turbocharged for 190 PS and 450 N·m, both to Euro 6. Buyers who wanted an engine of Stuttgart's own design had to wait for the X 350 d and its OM 642 V6 — and then not long, because Mercedes-Benz abandoned the whole project in May 2020, less than three years after production began. The OM 699 outlived the truck it was adapted for, still working in the Renault and Nissan models it had been built for in the first place.