19 fév 20

Test drive Mercedes-Benz C 300de: a plug-in hybrid that dares to opt for diesel

Call them stubborn, courageous, crazy or wise, but Mercedes-Benz believes diesel is a good option for its bigger PHEV models, starting with the C Class. It has a lot going for it from a rational point of view, but what’s it like on the road? And if it does fit the fleet bill, does it have enough assets to make fleets conquer their dieselphobia?  

Street cred (look&feel, driving experience, equipment): 8/10

The choice for diesel in this plug-in hybrid C Class is counter-current. Nobody else offers a diesel PHEV anymore. Then why does Mercedes-Benz? First of all, fleet vehicles in the D segment or above usually travel longer distances. Second, petrol doesn’t cope well with weight and air resistance. Third, Mercedes-Benz have adapted their ultra-modern 2-litre 4-cylinder with hybrid use in mind.

Diesels have a reputation for not keeping their manners - neither ecologically nor auditorily - when awakened, something that happens frequently in the case of a hybrid. Mercedes-Benz has however succeeded in mastering their OM 654 engine's vibrations and noise sublimely. Moreover, this diesel plug-in hybrid has a partial burning-off strategy for its particulate filter, enabling to eliminate the trapped particulate matter in portions when conditions are suitable.

As to the performance, the diesel engine sends 143kW (194 hp) and 400Nm to the rear wheels through a 9-speed automatic transmission, into which a 90kW/440Nm electric motor is integrated. Together the engine and motor achieve a system output of up to 225kW, while their combined torque is limited to a maximum of 700 Nm, available at just 1400rpm.

When both power units work together, accelerations reach sports-car levels. Still, you kind of feel disappointed when the diesel engine kicks in, either because you depress the accelerator pedal too enthusiastically or when the battery pack runs out of juice. Not that the diesel displeases – it is well-mannered and creates less decibels than some petrol plug-ins we have tested. Dynamically, the C Class strikes a convincing balance between comfort and agility, procuring satisfactory amounts of driving fun. 


As to the perceived quality of this C Class, it still justifies its price tag. It feels, smells and looks the part and at about €43k excluding VAT (Germany), it sits at the same price level as the BMW 330e touring but costs some 3,500 euros less than the Volvo V60 T6 PHEV, which does carry more standard trim and has all-wheel drive, but also feels less luxurious and refined. A Merc being a Merc, there is a multitude of (mostly expensive) personalisation options, the most relevant of which are grouped into packages.  

The HMI of the Mercedes C Class is still not an example of intuitive operation, but after a few days you more or less find your way in the jungle of commands and menus. We would suggest opting for the 12.3-inch digital dashboard, the Media Control Touch pad and the Smartphone integration package (Apple Car Play, Android Auto, text-to-speech). As to the Audio, the Burmester surround sound system is definitely worthwhile given its relatively reasonable price, but it is unacceptable that you still have to pay extra for DAB.

Fleet cred (Safety, eco-credentials, TCO): 8/10

The 300d engine already complies with the Euro 6d standard. In June last year, German car magazine Auto Motor und Sport road-tested the car and wrote: "With a measly 13mg of NOx, it goes to the top of our ‘Mr Clean’ hit list.  […] The two-litre diesel called the OM 654 has been systematically trimmed for reduced emissions. The NOx problem of many cities is therefore bound to be resolved as soon as more new cars are registered".

If that’s not reassuring enough, you should know that once the driver has input a destination into the navigation system, the battery charge is kept available for driving through towns and cities, while any regeneration of the particulate filter needed preferably takes places on motorway stretches. To maximise electric driving, the Eco Assist prompts you to come off the accelerator when you’re approaching a roundabout, for instance, so the battery can regenerate. Also, the haptic feedback in the accelerator informs the driver when further acceleration is only possible by activating the diesel engine.

Out of curiosity and in the interest of fleet managers worried about the worst-case fuel consumption, we drove 200km on the motorway – at legal speeds – with the battery depleted. The result was a surprisingly low 5.6l/100km. So even if you run out of electricity after roughly 40km, there is no monstrous fuel bill to fear. The 13.5kWh battery can be charged in about 2 hours at a wallbox or public charging station thanks to the 7.4kW on-board charger – which is double the capacity of most competitors.

It looks as if there is hardly anything to hold against the C 300de Estate. We do however find it almost unbelievable that Mercedes-Benz was unable to better integrate the battery pack, resulting in a huge bulge in the boot between the rear axle and the rear seats. Clearly, this compromises the practicality of this Estate. Also, we find it inappropriate for a safety-oriented brand like this to ask money for systems like a blind spot monitoring system and lane keep assist.

Bottom line: 16/20

Yes, this is a convincing offer for both the fleet manager (TCO, eco credentials, safety) and the company car driver (BIK, driving fun, charging speed) with a nice budget. The word face-palm comes to mind if you look at the 'battery-bulge' in the boot, though.   


  • Unique offering: 40km zero emission, frugal on motorways
  • Smooth performance, highly intelligent energy recuperation
  • Interesting TCO for high-mileage drivers: low actual fuel consumption
  • Eco credentials: Euro 6d compliant, diesel adapted to hybrid use


  • Bulge in the boot compromises practicality
  • DAB and some basic ADAS not standard
  • HMI not the most intuitive
  • Expensive options inflate the price tag 


Authored by: Dieter Quartier