The OM651 engine family is an inline-four cylinder Diesel automobile engine from Mercedes-Benz introduced in 2008. The chief design goal was to create a common engine platform that maximized the part commonality between the engines manufactured by Daimler. One requirement of the design was its ability to be mounted in both longitudinal and transverse fitments. Emission standards and fuel efficiency were also driving design factors. The engine uses recirculated exhaust gas to reduce the oxygen in the cylinders to "starve" any reactions that would produce NO(x), enabling it to meet Euro 5 emission standards.
