The claimed fuel consumption figure on the C350e is 2,1L/100 km. Now, we all know these claims derived from the NEDC test method are highly conservative, particularly for hybrid vehicles. Can the C-Class plug-in hybrid surprise us and make a case for itself on efficiency alone?
During the city drive section of the route leaving East London, electric-only mode was mostly employed with a rare burst from the 2,0-litre, turbopetrol engine. The fuel consumption read-out hovered at an astonishing 3,0 L/100 km. But then we hit the highway…
Hybrid tech added
To create the C350e, Mercedes started with the C250, which is powered by a 2,0-litre turbopetrol delivering 155 kW and 350 N.m. The engineers then added an electric motor of 60 kW and 340 N.m (total power and torque figures of 205 kW and 600 N.m, respectively) in the transmission housing and included a clutch to be able to disconnect the internal combustion engine from the drivetrain during strictly electric operation. Electrons are supplied by a 6,2 kWh battery pack housed in the boot over the rear axle. This exercise added 271 kg in total, with 100 kg attributed to the battery pack alone. The boot capacity thus shrinks to a still usable 355 dm3.
Driving technique
Driving the C350e is no different to piloting any other C-Class, except that there is no engine sound on start-up. The driver can choose between several driving modes as well as different hybrid modes, including Hybrid, E-mode (for electric driving), E-save (to keep the battery charge for later use) and Charge (which charges the battery via the petrol engine). A clever technology is the haptic feedback accelerator pedal that informs the driver when they are about to exceed the capability of the electric powertrain and the petrol engine is ready to kick in. The satellite navigation system monitors the topography of the road ahead to enable the powertrain control system to optimise vehicle efficiency by pre-empting inclines and employing regenerative charging on the downhills without driver intervention.
Electric only
Mercedes claims that the C350e can drive up to 31 km and up to speeds of 130km/h on electricity alone. As it is a plug-in hybrid, the battery can be charged at home in approximately two hours and this negates the efficiency loss of conventional hybrids having to convert fuel into electric charge when regenerative braking is not available. This allows the owner of the C350e with a short commute to work to drive mostly in electric mode and only use the petrol engine on longer journeys.
Electric boost
The C350e is more responsive to drive than the C250 as the electric motor provides a power boost when, for example, swift overtaking ability is needed. This boost capability enables a sprint to 100 km/h from standstill in a brisk 5,9 seconds. Subjectively, it feels as if the standard air suspension has a harder job to provide that “magic carpet ride” compared to non-hybrid models that feature a similar suspension set-up.
Summary
At R804 900, it is hard to make a case for the car in the South African context where there is little incentive to invest in an environmentally friendly vehicle. The fuel readout climbed to 8,5 L/100 km on the motorway towards Port Elizabeth, which eroded the green credentials and showed that hybrids do not make sense on longer journeys. The last figure will easily be beaten by a C220d at a considerably lower price and may therefore be a wiser option in the long run.
