The engine that lent a new level of oomph and eco-cred to Mercedes’ top choice AMG has failed to cut it with enthusiasts.

ASTOUNDING punch and status as the first C63 to seamlessly accomplish sub-10 litres’ per 100km economy - and also cement as a genuinely eco-friendly choice - hasn’t been enough to save it: Mercedes-AMG is set to reverse its decision to downsize its hero car’s engine to a hybrid four-cylinder.

The British motoring magazine Autocar is among motoring media to report firm view that the Mercedes-AMG C63 will from 2026 ditch that 2.0-litre turbocharged PHEV it released here with last year.

You think you read about that already? You read wrong. Reports last year said the four was being ditched for a return to V8.

That’s not true in respect to the C63, or the GLC 63. Those are going to pick up a 3.0-litre in-line six-cylinder engine, still with plug-in hybrid technology.

The heart transplant will lower the cars’ kapow and times into the car’s scheduled mid-life facelift - though the latest C63 is a relatively recent appearance here, it will by then have been in production for more than three years, having been on sale in Europe for at least a year prior to NZ launch.

Even though it derived from a unit that turned its first provision AMG 45 into a cult hot hatch, the high-output four-cylinder M139 engine (above) and electric motor set-up was always a hard sell to C63 fans.

Credibility as the most powerful engine ever planted into the car - AMG citing it being good for 500kW and a whopping 1020Nm of torque - didn’t wash with enthusiasts; what has historically been the most popular of the AMG models has simply not resonated in current format, the latest reports say.

The six-cylinder PHEV set-up will be derived from that of the E53 and GLE 53 and is expected to produce more than 480kW and 880Nm.

So what about the V8? The CLE 63 Coupé and Cabriolet will, according to Autocar, be fitted with a 4.0-litre twin turbo V8, specifically a flat-plane-crank version of AMG’s M177 used in models like the last-gen C63 since the mid-2010s.

However, that plan couldn’t play out for the sedan and SUV as they base off the current C-Class, which having been designed with just four- and six-cylinder engines in mind, would reportedly require an expensive redesign in terms of the engine bay and structure to accommodate a V8.

Autocar says the incoming C63 drivetrain will do away with the electric motor mounted to the rear axle and instead use a motor between the engine and transmission. This should conceivably free up boot space, which at the moment is equivalent to that from a Suzuki Swift.