Thomas Weber has a challenging but hugely rewarding job. It involves predicting the technological future for one of the world’s most prestigious car companies, and then leading its implementation at a time when the motor car is on the cusp of the biggest burst of change since Karl Benz’s pioneering little three-wheeler clattered into crude life 124 years ago.
Weber freely admits, however, that as the Daimler executive in charge of research and development, he is keeping his options open when it comes to picking winners in the industry’s urgent campaign against global warming.
Within the Daimler stable, Mercedes is pursuing just about every form of CO2-reducing powertrain going – from “parallel” hybrids such as Toyota’s Prius, through “range-extenders” similar to the Chevrolet Volt (which was due to be launched next year but whose future is now clouded by General Motors’ bankruptcy), to entirely battery-powered cars, those that run on fuel cells and those that rely on other ways of using hydrogen, whose only exhaust emission is water vapour.
In the next few months the first such “new-tech” car to come out of the Mercedes box will go on sale. It is a hybrid version of the recently updated S-Class, by far the world’s biggest-selling luxury saloon.
Toyota’s top-end hybrid, the Lexus 600h, comes in both right- and left-hand-drive versions. But has Mercedes got a point? Is there a small enough difference between the fuel economy and CO2 emissions of the S 400 Hybrid and the diesel for it not to be worth creating a right-hand-drive hybrid?
A first glance under the bonnet of the S 400 will leave you wondering what all the fuss is about. It looks a perfectly ordinary engine bay, with a 3.5 litre V6 petrol engine in the usual place and the battery roughly where you would expect to find it, tucked away in a corner. Except that, out of sight inside the engine and transmission casing, a powerful electric motor surrounds the crankshaft. And, despite being roughly the same size and shape as a conventional car battery, this one is vastly more powerful and is the heart of the world’s first fully commercialised hybrid car to use lithium-ion battery technology. That gives the Mercedes an advantage over the Lexus: the latter has a much larger and heavier nickel metal hydride battery pack, which takes a big bite out of the boot space.
Like the Lexus and Toyota’s Prius, the S 400 is a “parallel” hybrid. At low speeds around town it can be driven on the zero-emissions battery pack alone. On the open road it can cruise on its 279hp petrol engine, or, for higher speeds and overtaking, both petrol and 20hp electric motors can work together. Deciding which to use and when requires nothing of the driver – it’s all computerised. That 20hp might not sound much and it isn’t. What matters is the electrical unit’s torque: nearly 120lbs ft from standstill, almost half as much as the torque of the petrol engine. This makes take-off very lively, although nowhere near as lively as the autobahn-storming Lexus 600h – but then the Japanese maker has opted for a hugely powerful 439hp petrol engine.
But what about the diesel S-Class with which Mercedes says its hybrid should be compared? It is, to be fair, pretty close. In spite of hybrid cars’ reputation for frugality, the S 400 can’t quite match the diesel on economy: 35.8 miles per gallon on the EU combined test cycle compared with the diesel’s 37.2. The hybrid is slightly faster – 7.2 seconds to 62mph against 7.8 seconds. Both have top speeds of 155mph. Subjectively, their on-road performance is on a par. The hybrid would fare somewhat better in terms of UK company car taxation, with its CO2 emissions of 186 grammes per kilometre falling below the diesel’s 199. All revised S-Class models have improved fuel economy due to a stop/start system that cuts and restarts the petrol engine automatically at standstill.
There is no performance chasm between them, then. But the same cannot be said for prices. These have not been finally set, as none of the new S-Class models goes on sale until the autumn. But, based on about £60,000 for the current diesel model, the new diesel will be at least £12,000 cheaper than the projected €85,000 (£72,000) price of the hybrid.
The driving experience is not dissimilar. The hybrid is uncannily quiet but both more than meet the standards of refinement required of a successful luxury car contender. And revisions to the whole S-Class range can only further cement its market-leading status, with 270,000 of the current models sold since their launch in 2005. There is a lot of innovative new technology, not least an “active body control” system that automatically stabilises the car in strong crosswinds. The leather interior has been made more plush and the efficiency of all the engines has been improved.
In short, it’s hard to escape the conclusion that the Brits really aren’t missing out on much – except, perhaps, the more virtuous feeling that might come from puffing out 13 fewer grammes of CO2 per kilometre. But there are compensations – not least some 12 grand still safely in the bank.
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The details
Test match: hybrid v diesel
How much
£74,000 (approx) S 400 Hybrid; £60,000 (approx) S 350 CDI BlueEfficiency diesel. On sale: autumn, but hybrid not coming to UK
How fast
0-62mph 7.2 secs (hybrid); 7.8 secs (diesel). Top speed 155mph for both
How thirsty
35.8mpg (hybrid); 37.2mpg (diesel)
How green
186g CO2/km (hybrid); 199g CO2/km (diesel)
Also consider
(much faster) Lexus 600h, £84,730
Gallery: 2010 Mercedes-Benz S400 Hybrid Sedan
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