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The Mercedes S400 Hybrid makes petrol power a realistic mainstream option again for mainstream S-Class buyers. Jonathan Crouch drives it.

Ten Second Review

You might expect a big petrol-powered V6 Mercedes-Benz S-Class luxury saloon to be an expensive thing to run, but in the case of the S400 Hybrid model we're going to look at here, you'd be wrong. It matches the returns of the conventional diesel variant, doesn't cost much more and is powered by cheaper green pump fuel. It's a surprisingly compelling proposition.


If you're considering a full-sized luxury saloon, then you're probably not thinking of a hybrid version - but perhaps you should be. The running cost stats are compelling, even more so than those of the conventional diesels that most executives currently choose. And if you are to consider hybrid power, then it makes sense to turn to the brand offering the widest choice of options. That brand is Mercedes-Benz.
In this sixth generation S-Class model, the Stuttgart maker offers everything the automotive industry currently knows about hybrid technology. So there are petrol/electric, diesel/electric and even Plug-in hybrid powerplants from which to choose. The petrol/electric S400 we're going to look at here matches the running costs of the conventional diesel model. The diesel/electric delivers the balance sheet figures of a Fiesta-shaped supermini. And, as for the Plug-in Hybrid, well, the figures speak for themselves: 94.2mpg on the combined cycle and a CO2 return of only 69g/km. No other brand can match this. But then, no other brand makes a car like this s-Class. Let's use the S400 variant to check out its hybrid proposition in a little more detail.

Driving Experience

Unlike the entry-level S-Class Hybrid model, the diesel/electric S300 BlueTEC Hybrid, this S400 variant has a six cylinder petrol/electric engine. Just like the top S500 Pug-in variant in fact, though that car has a very different mechanical layout. Where the S500 Plug-in has a 329bhp 3.0-litre 'six' mated to a large electric motor that gives an 18 mile electric-only range, this S400 has a 306bhp 3.5-litre V6 mated to a much smaller 27bhp motor and only claims an electric-only range of around a mile. It's still a very efficient package though, with returns that all but match those of the conventional diesel model. Quick too, rest to 62mph taking 6.8s.
As with other S-Class variants, the standard air-suspended set-up with its 'Sport' and 'Comfort' Airmatic modes is vastly impressive in its ability to shelter you from the pock-marked mediocrity of our roads, with undulations and tarmac tears passing beneath you with hardly a murmur. This MK6 model can even be reasonably rewarding to drive when the going gets twisty thanks to superb body control from a stiffer chassis, the creation of which has been aided by the way this generation version has been developed as a long wheelbase saloon first, with the short wheelbase variant spawning from it. Normally, it's the other way around. This approach has given the car around 50% greater torsional rigidity.

Design and Build

This S400 Hybrid, like most S-Class variants, comes only in long wheelbase form, but at first glance, you don't immediately realise that for here, there isn't the slightly odd elongated look that characterises lwb versions of this car's competitors. That's because, unlike those rivals, it was originally designed around the longer bodyshape, rather than styled in shorter form, then stretched. The difference shows.
So you're free to simply admire the classic elegance centred in profile around this character line - what Mercedes rather awkwardly calls a 'Dropping Line' - that descends discreetly from the front to a rear section where this pronounced shoulder above the back wheel gives the rear end of the car a power-packed look. Talking of wheels, the 18-inchers are standard but to me look rather under-sized for the sheer enormity of this car. I'd specify 19-inch alloys instead.
Drop inside and owners of the previous generation version will notice the more spacious feel, with significant amounts of extra head, elbow and shoulder room in a less cluttered cabin that's a long way removed from the button-fest that many Mercedes owners are accustomed to. Rear seat passengers are even better provided for, as is appropriate in a car that many owners will want chauffeur-driven. They've 14mm more knee room and 9mm more shoulder room than they would have had in the old MK5 model and of course, in the kind of long wheelbase guise I have here, there's plenty of room to stretch out and relax.

Market and Model

Priced at around £70,000, this S400 Hybrid is a little nearer the cost of a base diesel S-Class than its diesel hybrid S300 BlueTEC stablemate and equals a base diesel S-Class variant's performance and running cost figures in even greater silence while using cheaper green pump fuel to drive a silky-smooth 3.5-litre V6. It's well equipped too, with Airmatic air suspension, metallic paint, alloy wheels of at least eighteen-inches in size, a rear parking camera with Parktronic Active Park Assist sensors front and rear, auto headlamps and wipers, power-folding mirrors, leather trim, electrically adjustable heated front seats, luxury automatic two-zone climate control, ambient lighting with a choice of seven colour settings, a lovely analogue dashboard clock, an auto-dimming rear view mirror, a multi-function nappa-leather-trimmed steering wheel and cruise control.
I also like the 'Magic Vision Control' windscreen wiper set-up that jets the fluid directly out of a wiper blade that's heated to prevent snow or ice forming on it in winter. Plus there's a super-clever LED Intelligent Light System that adapts itself to either country roads or motorways, turns with the corners and dips itself in the face of oncoming traffic at night. You also get the COMMAND Online system with media interface that offers Linguatronic voice control and SD card or USB compatibility.

Cost of Ownership

A decade ago, the kind of progress this sixth generation S-Class has made in terms of efficiency would have sounded like a utopian dream, yet the reality is that fuel consumption and CO2 emissions have been virtually halved in that time. A class-leading drag co-efficient that can be as low as 0.23Cd helps here. So do the weight savings brought about by use of aluminium in over 50% of this vehicle's construction. And the greater efficiency of Euro6-compatible engines that across the board are about 20% more economic than those in the previous generation line-up, this figure aided by fuel-saving electronic Direct Steering, low rolling resistance tyres and, as you'd expect, a start/stop system that cuts the engine when you don't need it, stuck in traffic or waiting at the lights.
As a result of all this, the petrol/electric S400 Hybrid delivers 44.8mpg and 147g/km, so virtually matching the returns you get from the ordinary diesel version. Unfortunately, you only get a tiny all-electric driving range of less than a mile.


This S-Class spearheads technological development, not only for Mercedes-Benz but for the automotive industry as a whole - and has done for decades. It's that important and is why this is - and will continue to be - the world's best selling luxury car. And, in hybrid terms, the leading choice in its segment.
With petrol/electric, diesel/electric and Plug-in hybrid options, this sixth generation S-Class will give its rivals quite a headache. This S400 petrol/electric variant may not be quite as cost-effective as its S300 BlueTEC diesel Hybrid stablemate, or as jaw-droppingly efficient as the S500 Plug-in Hybrid version but it's a very good all-rounder, more refined than the S300 and much more affordable than the Plug-in Hybrid model. Whatever your preference though, if you're thinking of buying an S-Class, you need to try the Hybrid option. It'll surprise you.

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