Engine: 2.15-litre four-cylinder turbo-charged diesel
Transmission: seven-speed wet-clutch automatic gearbox incorporating electric motor
Power: 204 PS at 4,200 rpm between 1,600 and 1,800 rpm (diesel engine), 27 PS (electric motor)
Torque: 500 Nm between 1,600 and 1,800 rpm (diesel engine), 250 Nm (electric motor)
Fuel consumption (combined cycle): 65.7 mpg
CO2 emissions: 109 g/km
Top speed: 150 mph
Acceleration (0-62 mph): 7.5 seconds
A top speed of 150 mph, 65.7 mpg and 109 g/km in official tests – and all in a car with a roomy five-seater body. A few years ago that would have been considered impossible, but those are the figures that leap out from the spec sheet of the latest addition to the Mercedes E-Class range, the diesel-electric E 300 BlueTEC Hybrid – although they do rely on prospective owners opting for unfashionably downsized 16-inch wheels to get below the 110g/km mark.
The E 300 BlueTEC Hybrid’s drivetrain brings a modest weight penalty of 60 kg, all of it at the front, because Mercedes has managed to squeeze all of the hybrid-specific parts, including the battery, under the bonnet, so that they don’t interfere with passenger or luggage space. That might not sound great for balance or handling, but as one of Mercedes top powertrain engineers, Jürgen Döring, pointed out when he briefed me on the car’s finer details, its four-cylinder-diesel-plus-electric hybrid drivetrain is really an alternative to a heavier conventional engine with six or more cylinders.
It’s hard to argue with that. On the road, the E 300 BlueTEC Hybrid’s drivetrain is enormously impressive, with the combined power, and in particular torque, of the diesel engine and electric motor providing very strong acceleration indeed. The torque output of the diesel engine alone, at 500 Nm, far exceeds that of most internal combustion engines on road cars; the electric motor, which is incorporated into the seven-speed automatic gearbox, has maximum torque of 250 Nm but the peak torque for the system as a whole is a still impressive 590 Nm.
For all that, though, driving the E 300 BlueTEC Hybrid provides a slightly underwhelming experience, if only because, extra performance apart, it feels quite like any other Mercedes four-cylinder diesel car, which is to say, not very "hybridy". There’s no real lurching, clunking or whirring to signify transitions between electric and diesel operation – although there are the usual hybrid dash displays that show you what’s going on. Nor does it seem to go in for significant periods of electric-only running in normal driving.
For the rest, the E 300 BlueTEC is much the same as any other E-Class - roomy and mostly comfortable, although our test car had a rather bumby ride over speed bumps and ridges, which was all the more surprising given that it was fitted with those smaller wheels. The cabin wasn’t bad – a bit tired and not as good as those of premium rivals such as Audi, BMW and Jaguar but better than some of Mercedes' efforts of a few years ago. Overall, though, there’s a general feeling that when it comes to the detail, this car needs the mid-life update that's supposed to be on the way, just to give it a bit of a lift. But the hybrid drivetrain is just fine the way it is.