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Removing the petrol engine from the Mercedes-Benz S-Class equation leaves you with a whole lot of nothing.
When the Mercedes-Benz S500 plug-in hybrid limousine arrives on our shores late next year (matching the $285,000 pricetag of the S500 petrol-only V8) one of the quietest cars in the world will become even more hush.
It will be the premium German brand’s first production model sold locally that can be plugged into a powerpoint and run solely on the silken whirr of electricity; that is provided you keep a light right foot.
The S500 doesn’t prioritise electric running quite like a Holden Volt, for example, which uses only its battery-powered motor until it runs low on electricity then uses the supporting petrol engine to recharge it.
Rather the Mercedes-Benz solution – as with the Porsche Panamera e-hybrid and even the Mitsubishi Outlander PHEV – is to prioritise electric running where possible, but use the supporting petrol engine as a performance booster.
For worse or better, if you put your foot down slightly in the S500 on a hill the 3.0-litre twin-turbocharged V6 petrol engine will kick into life.
Worse, because it ruins the silence and affects ultimate economy.
Better, because if you flatten the accelerator it feels as though you’ll achieve the 5.2 second 0-100km/h claim, using all of the combined 325kW of power and 650Nm of torque – a not-so-direct equation of adding the petrol’s 245kW/480Nm with the electric motor’s 85kW/340Nm.
It takes just two hours to fill the S500’s 8.7kWh battery pack via a fast charge station, but you can also use a standard household power socket if you have double the time to wait.
For that you get a claimed 33km of driving range that helps this big Benz hybrid achieve consumption of just 2.8 litres per 100 kilometres on the lab-tested combined cycle.
The interior of the S500 plug-in hybrid is exactly like every new Mercedes-Benz S-Class – beautiful, detailed, sumptuous – so we’ll focus on the few differences of this frugal new model.
There’s an E-Drive gauge under the left side of the regular tachometer indicating how much throttle you have to give before the petrol engine will kick in. When the blue bar graph fills to the brim, then the tacho needle will flutter to life and take the baton.
On the other side of the tacho there’s a Charge bar graph that tells you how much regenerative energy the batteries are chewing on when you’re coasting or braking.
Four modes are available in the main system – Hybrid, E-Mode, E-Save and Charge. Hybrid is essentially a default mode; E-Mode prioritises electric running though not exclusively; E-Save lets you store battery capacity for city running, for example; and Charge uses the petrol engine to recharge the batteries.
While legroom and seat comfort is capacious as ever in the S-Class, the same can’t be said for boot space, which due to the installation of the batteries falls to 395 litres – just 15L more than a Volkswagen Golf. There’s also no split-fold rear seat, though Mercedes-Benz insists the S500 plug-in hybrid can fit a single golf bag in.
Mercedes-Benz also says this is the no-compromise plug-in hybrid, but in a world of increasingly numerous eco-conscious offerings it’s worth noting that even a Mitsubishi Outlander PHEV at one-fifth of the price claims 52km of driving range and with no impact on boot space.
The Japanese SUV certainly doesn’t have the performance of the S500 plug-in hybrid, but nor does it have the pricetag.
Getting out of the peak hour traffic at the international launch at Stuttgart, Germany, the S500 plug-in hybrid purrs along on effortless, silent torque. Initial impressions are that this 2215kg limousine doesn’t feel as responsive as the 2015kg 5.5-litre twin-turbo petrol V8 model that wears the same S500 badging and pricing, and claims a half-second quicker time to the 100km/h benchmark.
It’s not just the outright acceleration that suffers, but in the seven-speed automatic transmission’s normal mode there’s delayed response to a quick prod of the throttle when overtaking – probably because the petrol engine first needs to fire.
The sound the V6 makes is also more strained and thrashy compared with the creamy, burly smoothness of the engine with two extra cylinders, though that’s a price to pay for using less than a third of fuel (the V8 claims 9.2L/100km; the hybrid just 2.8L).
But the hybrid system switches seamlessly between petrol and electric power on the move, and will retain enough juice in the cells of the batteries to keep the electric motor boosting the performance.
The sat-nav even can work out the best way to handle an upcoming gradient, and a ‘haptic’ function pulses the accelerator pedal twice when the system detects it can coast and recuperate energy – smart, but very unnerving. Similarly, the click on the accelerator pedal as you switch from electric to petrol power is strange.
After 32 kilometres and 54 minutes of driving time at an average of 35km/h, the S500 plug-in hybrid is out of electric range. While that sounds like we’ve achieved the claim, the petrol engine also came in by enough to use 1.1 litres of petrol over that time as well (or 3.4L/100km).
When the power you’ve gained from a powerpoint is out, the car is left to its own devices to either capture energy from the brakes or use the petrol engine as a generator. It also marks the point where consumption rises sharply.
Outside of the city, after 84km and 1 hour 44 minutes driving time at a lifted 44km/h average, the S500 plug-in hybrid has slurped 7.0L/100km. This, again, is impressive, however continue driving and consumption continues to rise as the electric driving portion of the total running becomes smaller.
As less focus is placed on the electric driving, the S500 plug-in hybrid drives like the less impressive twin of the petrol-only S500.
For that executive who needs (his chauffeur) to string corners together quickly between the expressways the S500 plug-in hybrid seems to be more reliant on the grip levels of its excellent 18-inch Michelin Pilot Sport 2 tyres than the lighter V8.
The steering remains pleasantly light and incisive, however, the ride is supremely plush in Comfort and only slightly firmer in Sport, and then there’s the tranquility – this Mercedes-Benz is whisper quiet at speed and eerily silent when the petrol engine is off.
The level of technology available on the S-Class remains outstanding, though some of it will likely still come at a cost.
Seen on the 12.3-inch TFT screen, the Mercedes-Benz NTG5 Comand system permits access to the internet, apps for remote connection of the air conditioning for example, and Google Earth/Street View. In the S500, there’s also 250Gb of storage, WLAN, digital radio and TV, an SD card reader, two USB ports and of course Bluetooth.
Protecting those assets (and its occupants and others) are a 360-degree camera, blind-spot assistance, adaptive cruise control, drowsiness detections, full LED lighting with auto high-beam and a system dubbed Pre-Safe – which recognises pedestrians and other objects and will brake the car if the driver fails to.
Placing aside the economy benefits of the S500 plug-in hybrid, the petrol V8-engined S500 is the better drive. However it’s difficult to simply place aside this model’s claimed economy that totals only a third of the traditional model’s when the performance is so similar.
While for the price we’d expect greater range and less boot space compromise, this Mercedes-Benz S-Class proves that indulgence and eco-consciousness can co-exist.