The rivalry between the BMW 3 Series and the Mercedes C-Class is one of the longest in the car industry. If you are interested in how a car drives it has always been pretty clear cut, you buy the BMW. However with the latest C-Class closer than ever in the driving stakes the decision is a lot harder than it used to be, and the latest curve ball is that the Mercedes has adopted a diesel engine which makes an interesting point of differentiation.
The latest battle ground is the high tech world of plug-in hybrids. The Mercedes system uses a slim electric motor integrated into the 9 speed automatic gearbox. An additional clutch allows the electric motor to power the car independently or in combination with a 2 litre twin turbocharged diesel unit. A useful 13.5 kWh (net) lithium-ion battery provides enough juice for between 20 – 34 miles of pure electric running with the system reverting to hybrid after this point. In order to support the bigger battery the ‘de’ gets a 7.2 kW on-board charger rather than the plug-in hybrid norm of just 3 kW. That allows a full recharge in 1.5 hours.
The combined system provides a mighty 516 lb ft of torque which fires the C Class to 62 mph in under 6 seconds. In pure electric mode performance remains strong with a usefully high top speed of 81 mph allowing you to run in EV mode anywhere.
To help you to maximise electric running the system can use a sat nav route to decide when to recharge, save or use the battery. It can also make suggestions to the driver through the haptic accelerator pedal which provides pulse points to suggest lifting off to coast up to a car in front, and a resistance point to tell you when further application of the accelerator will start the diesel engine.
If you want more control you can select E-mode, E-save, or Charge manually in addition to all the usual drive configurations of gear change speed, suspension, accelerator and steering settings. The system is also capable of ‘sailing’ where the petrol engine is de-clutched to allow the car to roll at speeds up to 81 mph. By using the radar system the C-Class can decide when sailing or regenerative braking is the best option and also when to trigger the haptic accelerator to maximise the effect.
The plug-in C-Class is a technical tour de force, but is it enough to dethrone the 330e? Not quite. The BMW offers a longer electric range, is slightly better to drive, and despite a power deficit is only 0.4 secs slower to 62 mph. It also happens to be a chunk cheaper so whilst the Mercedes is a great car it has come up against a super foe in the shape of Munich’s finest.
Estimated real world range: 20 – 34 miles (electric)
Official electric range: 34 miles
Electricity consumption: 204 – 246 Wh/km
Battery pack: 13.5 kWh (usable) lithium-ion
Recharge time: 230v 5 hours; 7 kW wallbox 1 hour 30 minutes (10-100%)
Please note that CO2 emissions quoted for electric cars are not directly comparable to diesel and petrol cars. This is because CO2 emissions quoted are calculated by Green Car Guide and include the emissions created at the power station turning fuel (e.g. gas etc) into electricity and in transmitting and distributing the electricity to an end user. They do not include the actual production of the fuel (e.g. gas extraction and refinery emissions). Petrol and diesel emissions are supplied by car manufacturers and are based solely on the fuel burnt in the engine (tailpipe emissions) and do not include the production of the fuel or distribution to a fuel station. In practice this means that electric car emissions are over-estimated relative to petrol and diesel. For instance if an electric car, a petrol car, and a diesel car are all reported to emit 100 g/km CO2, the electric car actually has lower emissions.