The combustion engine delivers 208bhp at 5500rpm and 258lb ft of torque, while the electric motor provides an additional 80bhp and 251lb ft. Altogether, the combined system output is set at 275bhp and a sturdy 442lb ft, giving the C350 Plug-in Hybrid some 74bhp and 214lb ft more than the C250, with which it shares its petrol engine.
The combined reserves are channelled through a modified version of Mercedes’ widely used 7G-Tronic seven-speed automatic gearbox to the rear wheels. It incorporates an automated clutch, which is opened during electric running to reduce mechanical drag and provide added coasting potential on a trailing throttle. As with AMG’s SpeedShift unit, the clutch is also used as a substitute for a conventional torque converter during the step-off phase when the combustion engine is in use.
Mercedes is yet to provide a weight figure for the C350 Plug-in Hybrid. However, official performance figures reveal it is quite swift in a straight line, with a claimed 0-62mph time of 5.9sec for the saloon and 6.2sec for the estate. Top speed is put at 155mph and 153mph respectively.
The driver can choose between five different driving modes: Economy, Comfort, Sport, Sport Plus and Individual. On top of this, there are four operating modes: Hybrid, E-mode, E-save and Charge. Each mode varies the energy recuperation, coasting and gearbox characteristics, with E-mode allowing the C350 Plug-in Hybrid to run in electric mode for a claimed distance of up to 19.3 miles on a fully charged battery.
This extended electric range translates to headlining combined consumption of 134.5mpg for both the saloon and estate on the controversial European test procedure, providing the C350 Plug-in Hybrid with respective CO2 figures of just 48g/km and 49g/km.
Energy for the electric motor is provided by a 6.2kWh lithium ion battery mounted within the floor of the boot, reducing capacity by 15 litres (to 335 litres) in the saloon and by 30 litres (to 350 litres) in the estate compared with other C-class models.
Compatible with both plug-in and recuperated recharging, the battery, which officials suggest weighs around 100kg, is water-cooled and comes housed in a steel cradle for added safety.
Mercedes claims a recharge time of between two hours on regular 240V/13A household mains electricity and 1 hour 45 minutes on a 240V/16A system. The charge status of the battery along with a standard preset air conditioning function can be monitored via the internet.
To help the driver to maximise the efficiency of the C350 Plug-in Hybrid’s petrol-electric powertrain, Mercedes has fitted it with a so-called 'haptic accelerator' as standard.
Already introduced on the S500 Plug-in Hybrid, it varies the amount of resistance within the accelerator, signalling to the driver that maximum electric performance has been attained and an impending introduction of the combustion engine. It also provides an impulse through the accelerator pedal to suggest the driver could achieve fuel savings by lifting off the power when the car's radar system detects you are running too close to the car ahead.
Underpinning the C350 Plug-in Hybrid is a specially tuned version of the C-class’s four-link front and five-link rear suspension. It comes as standard with self-levelling rear air springs and adjustable damping control.
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Read our review on the latest generation Mercedes-Benz C-Class saloon
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