Mercedes-Benz S500 Plug-in Hybrid: 245kW-plus and less than 3.3L/100km

The Mercedes-Benz S500 Plug-in Hybrid has been shown ahead of its official debut at the Frankfurt motor show in September.

CarAdvice and other Australian media were among the first to see the S500 Plug-in Hybrid, which in long-wheelbase test-car form was rolled out for the first time at the Mercedes-Benz S-Class launch in Toronto, Canada â€" curiously, earlier waves of foreign media were not shown the car.

Mercedes-Benz revealed the production S500 Plug-in Hybrid will use a 3.0-litre twin-turbocharged petrol V6 engine, producing the same 245kW of power and 480Nm as it does in the E400 and S400.

Head of hybrid powertrains at Mercedes-Benz, Dr Uwe Keller, wouldn’t be drawn into naming outputs for the accompanying electric motor, except to say that power is “quite high” and, compared with the plug-in Porsche Panamera’s 70kW electric motor, the S500 Plug-in Hybrid will have “definitely more. More in power and more in torque.”

That clearly indicates a combined system output of around 300kW, plus much more than 500Nm of torque, meaning the S500 Plug-in Hybrid could challenge the regular twin-turbo-V8 powered S500 as the quickest S-Class in the range, at least until the AMG models arrive. The S500 V8 claims 0-100km/h in 4.8 seconds, two seconds quicker than the S400 Hybrid that uses a non-turbo 3.5-litre petrol V6 with a tiny 20kW electric motor.

The electric motor in the S500 Plug-in Hybrid is fed by an 8.7kWh battery pack â€" around a third of the kilowatt hours produced by a Nissan Leaf â€" handing the luxury limo an emissions rating of 75g/km of Co2 and fuel consumption of around 3.2L/100km.

Keller confirmed that the S500 Plug-in Hybrid can run silently on electric power only at up to 120km/h. He only hinted at the electric-only range, however, saying that “the range has not been certified [but] it will be similar” to the Porsche Panamera hybrid, which claims 32km of electric-only running.

“We gathered a lot of data from our S400 hybrid … and we were looking at how people were using these cars,” he added.

“What we found out was that about 95 per cent of these are using a single range less than 20 miles. So that gives you some thought about what range we should have for this [S500 plug-in hybrid] car”.

The S500 Plug-in Hybrid can be charged via a household power socket, taking “up to two hours” to fully recharge its batteries.

The plug is located on the lower-right side of the rear bumper, but the batteries are located in the boot, hindering capacity compared with other S-Class models, even the petrol-electric non-plug-in hybrids.

As with other Mercedes-Benz hybrids, a clutch pack sits behind the internal combustion engine to disconnect the engine from the electric motor, which is located just ahead of the seven-speed automatic transmission.

Keller confirmed that Mercedes-Benz looked at using the same naturally-aspirated 3.5-litre petrol V6 engine used in the S400 Hybrid for the S500 Plug-in Hybrid but said that using the twin-turbocharged 3.0-litre V6 did not significantly change the emissions output.

“You don’t need it [twin turbos], but if you want to have it [the S500] on the one hand as a very efficient, but also a very powerful vehicle, you cannot use naturally aspirated you must turbocharge,” he told.

“The thing is you have to consider the technology you use with the bi-turbo.

“Going from naturally-aspirated to turbo didn’t really have an increase in fuel consumption.”

Keller also said that he expects to “bring this [plug-in hybrid] technology down to smaller engines” in the future, paving the way for future Mercedes-Benz production models to use even less fuel and produce fewer emissions than the S500 Plug-in Hybrid.