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Mercedes claims it has created the world's most efficient luxury car.
The company has been introducing more and more hybrids to provide bigger efficiency gains, and the new S500 Plug-in hybrid is its latest fuel-saving flagship.
Offering the power of a V8 and the ability to average an astonishing 101mpg while emitting just 65g/km of CO2, the 442hp model can sprint to 62mph in just 5.2 seconds. All this from a car that is road tax-free and slips quietly into the 5% BIK tax bracket.
The advances come from its state-of-the-art plug-in hybrid hardware that combines a 333hp 3.0-litre V6 twin-turbo petrol with a punchy 116hp electric motor.
In electric mode alone it's possible to cover around 20 miles without a drop of petrol. This means that with the help of chargers at home and work (it takes between two and four hours to charge fully) a whole week's worth of commuting could be completed without using any fuel.
To help the big Mercedes drink as little petrol as possible the firm has developed fascinating new tech that uses the navigation system, radar sensors and even the car's camera to predict what lies ahead. Then it decides when to run electric-only or use the petrol power. This means it coasts down hills and leaves electric running for the city. There's even something called a 'haptic' throttle pedal that prods back through the pedal to tell you when you should lift off and save fuel.
So what's it like? In electric mode it's more refined than even a Rolls-Royce while offering effortless performance, although our car would pause before deciding to give you the full 442hp. Once awoken there's even a nice V6 snarl - far more pleasant than a rattly diesel.
Behind the wheel, the S-class remains our favourite luxury car - it won the category prize in BusinessCar's 2014 Awards - although the hybrid is noticeably more nose-heavy than the standard saloon, but wind back the pace and you'll love the cosseting ride, world-class cabin and relaxing progress.
Apart from the punishing extra P11D cost over the diesel, the only real sacrifice is a boot almost a third smaller and the fact that on our drive we could only manage a diesel-rivalling 37mpg (others, though, cracked 50mpg.)
Model price range
Service, maintenance and repair
Vehicle Excise Duty
Cost per mile
BIK 20/40% per month
Faster, more refined than a diesel, and almost as efficient