The new Mercedes M252 engine, featuring a more powerful mild-hybrid system, is built in China. But how much Mercedes engineering is actually in this engine produced at Geely’s new plant in China? Here’s a detailed analysis.
Mercedes has collaborated with other manufacturers on small-displacement engines before. Previous examples include the 1.5-liter diesel and the 1.33-liter gasoline engines sourced from Renault for the former compact model range based on the MFA II platform.
However, Mercedes quickly discontinued the 1.5-liter diesel because, despite modifications made by Mercedes engineers, it failed to meet the company’s standards. It was replaced by a detuned version of Mercedes’ well-known 2.0-liter OM654 diesel.
By contrast, the 1.33-liter gasoline engine, combined with a mild-hybrid system, is still in production for the A-Class, which continues to be based on the previous platform.
For the new generation of compact models built on the MMA platform, Mercedes ended its cooperation with Renault and instead partnered with Geely, the Chinese automotive group that owns nearly 10% of Mercedes-Benz.
This marks the first time that a Mercedes model built in Germany is powered by an engine manufactured in China. Behind the M252 designation is a new 1.5-liter engine with 48-volt mild-hybrid technology, which debuted in the new CLA and is also used in the new CLA Shooting Brake and GLB.
According to Mercedes, the M252 engine was engineered by Mercedes and is manufactured in China by Aurobay, Geely’s powertrain division.
A Mild-Hybrid System Almost as Powerful as a Full Hybrid
The 48-volt hybrid system represents the second generation of Mercedes’ mild-hybrid technology. Instead of being belt-driven, the electric motor is integrated directly into the eight-speed 8F-eDCT dual-clutch transmission together with the inverter.
As a result, the engine-transmission unit is extremely compact. The engine itself is relatively short thanks to the small distance between the cylinders, while the transmission housing is also very narrow.
The electric motor integrated into the transmission also serves as the starter motor, eliminating the need for a conventional starter.
In addition, the air-conditioning system uses an electrically driven compressor that can provide cooling or heating even when the combustion engine is switched off or the vehicle is operating in electric mode. Consequently, a belt-driven air-conditioning compressor is no longer necessary.
The 48-volt battery has an unusually large capacity for a mild-hybrid system. Using NMC chemistry and offering a gross capacity of 1.3 kWh, it powers an electric motor that is also exceptionally powerful for this type of system.
Producing 30 PS and 200 Nm, the electric motor can propel the vehicle on its own over short distances and at low speeds. This is highly unusual for a conventional mild hybrid, where the electric motor normally cannot drive the vehicle independently.
When little power is required, the vehicle can coast at speeds of up to 100 km/h with the combustion engine disengaged and switched off. Energy recuperation is available in all gears, with a maximum recuperation output of up to 25 kW.
Like other Mercedes engines, the M252 features an all-aluminium crankcase and NANOSLIDE-coated cylinder liners. The cylinder head partially integrates the exhaust manifold, while the turbocharger uses a segmented turbine with a switchable flow path that directs exhaust gases precisely to the turbine.
The M252 has been designed for maximum efficiency and therefore operates according to the Miller combustion cycle, in which the intake valves close earlier to reduce pumping losses under partial load. It also features a high compression ratio of 12:1.
Power Outputs
The M252 is available in the CLA, CLA Shooting Brake and GLB in three power levels, all featuring the 48-volt mild-hybrid system:
- CLA/CLA Shooting Brake/GLB 180
- CLA/CLA Shooting Brake/GLB 200
- CLA/CLA Shooting Brake/GLB 220
The 200 and 220 versions are also available with 4MATIC all-wheel drive.
The combustion engine produces:
- 136 PS in the CLA/GLB 180
- 163 PS in the CLA/GLB 200
- 190 PS in the CLA/GLB 220
Because the electric motor is integrated into the transmission rather than driven by a belt, its output is combined directly with that of the combustion engine, much like in a full hybrid. As a result, total system output reaches:
- 156 PS in the CLA/GLB 180
- 184 PS in the CLA/GLB 200
- 218 PS in the CLA/GLB 220
First Driving Impressions
We had the opportunity to test the new Mercedes CLA 200 and noticed the “Made in China” inscription on the timing chain cover. While such a label may not immediately inspire confidence, the engine itself left a very positive impression.
Thanks to its unusually powerful mild-hybrid system, which performs almost like a full hybrid, the M252 feels like a significantly larger-displacement engine. It delivers immediate throttle response and provides ample low-end torque, where the contribution of the electric motor is particularly noticeable.
You can read more about our driving impressions of the Mercedes CLA 200 mild hybrid in our full road test.
