M264

The M264 is the longitudinal half of the second-generation four-cylinder family, and what matters about it is electrical rather than mechanical. Arriving with the facelifted W205 C-Class in 2018, it brought EQ Boost to a mainstream Mercedes-Benz: a belt-driven starter-alternator on a 48-volt system worth 10 kW and 160 N·m, used to cover the moment while the twin-scroll turbocharger builds pressure, to spin the engine to the right speed mid-shift so the automatic can change gear faster, and to recover energy on deceleration. The coolant pump runs off the same 48 volts, mapped rather than geared to crankshaft speed.

Two displacements were offered, and the smaller one made the argument. A 1.5-liter with EQ Boost replaced a two-liter in the C 200 and still produced 184 PS and 280 N·m — a downsizing that only worked because the electrics covered the shortfall down low. The 2.0-liter served the C 300, the E-Class from 200 to 350, the GLC, the CLS and the GLE 350, one engine badged as half a dozen different numbers depending on tune and market. Friction went to CONICSHAPE conical honing, the catalyst was mounted hard against the turbocharger to light off faster, and the M254 took over from 2020.