Why Mercedes-AMG's Record-Setting Four-Cylinder Engine Is Already on Its Way Out

Mercedes-AMG has long been synonymous with thundering V8 engines, but the performance division has always offered more variety than its reputation suggests. From inline-sixes to V12s, AMG's history is broader than many fans remember. Yet when the company tried to replace V8s in core models with a smaller, hybridized four-cylinder powertrain, buyers simply didn't bite.

0-liter M139—as part of a plug-in hybrid system. Despite churning out a combined 671 horsepower and 752 pound-feet of torque, the car has been met with lukewarm reception, and AMG has already confirmed it's moving on.

The M139 itself is an engineering marvel. In the C63 S E Performance, it cranks out 469 horsepower and 402 pound-feet of torque on its own, figures that rival many V8s. 3-second zero-to-60 time. But the tradeoffs are hard to ignore: the four-cylinder lacks the rumbling soundtrack that defined earlier C63 models, and the hybrid hardware adds roughly 780 pounds, bringing curb weight to nearly 4,900 pounds.

Buyers noticed. Dealers struggled to move inventory, discounts appeared quickly, and AMG CEO Michael Schiebe admitted the company overestimated customer willingness to embrace a four-cylinder C63.

In February, Schiebe revealed that the C63 will be replaced by a model powered by a six-cylinder engine with a lighter mild-hybrid setup, likely arriving with the C-Class's mid-cycle update for 2027. While he cited tightening European emissions regulations as the primary reason for abandoning the M139 in the C63, the market's chilly response almost certainly sealed the engine's fate.

For all its technical brilliance—the M139 features an electrically assisted turbocharger derived from Formula 1, direct and port injection, and a complex liquid-cooled battery—the powertrain's complexity and weight proved too much for traditional AMG fans. The four-cylinder experiment may be over, but it leaves behind a fascinating chapter in AMG's history: a record-breaking engine that buyers simply didn't want.