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Engine of the month

Mercedes 1.8 / 2.1 CDi OM651

The OM651 arrived alongside the 2008 C-Class (W204). Although fitted throughout popular models within the German brand, it was essential to keep up with the likes of BMW’s 2.0d Efficient Dynamics, which fuelled the C-Class’s arch nemesis – the BMW 3 Series.

Mercedes designated OM651 powerplants were tuned to either 134, 170 HP or for the higher specced models a 200 BHP version, badged C250 CDi. The engine was also used as a platform for the 1.8 CDi, and as you might expect, the two versions share many of the same components. As a combo, the pair powered a big proportion of Mercs’ on the road.

Introduced at the height of the diesel boom, the OM651 was never a class leader in terms of refinement but if you wanted an economical Mercedes with a bit of shove then it was the 2.1 or nothing.  Thanks to some decent sound deadening, the cabin was fairly insulated from what can only be described as a rattley Taxi to everyone outside the car.

Despite its foibles, the OM651 was an important unit that was utilised for a decade, found in hundreds of thousands of vehicles. This all adds up to a serious amount of business for the Aftermarket.

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