Mercedes S400 Hybrid (2009) review

Published:11 May 2009

Mercedes S400 hybrid
  • At a glance
  • 4 out of 5
  • 3 out of 5
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  • 5 out of 5
  • 5 out of 5

By Ben Barry

Contributing editor, sideways merchant, tyre disintegrator

By Ben Barry

Contributing editor, sideways merchant, tyre disintegrator

Mercedes always strives for its S-class to be at the technological cutting edge, so it must have been pretty miffed when Lexus beat it to market with its S-rivalling, hybrid-powered LS600h. This, then, is Mercedes’ riposte: the S400 Hybrid.

Brilliant, an S-class hybrid! When do I get mine?

Ah. Yes. Thing is, you won’t, not unless you steer from the left. The Germans won’t invest in right-hand drive production, pointing out that 80% of Brits will take the 350 CDI, while the Japanese often order S-classes in left-hand drive anyway because, for some reason, many see it as more prestigious. As for the poor Australasians and South Africans – well, they weren’t even mentioned.

Whatever the story, I’d say we’re being short-changed, and that the 80% of Brit diesel buyers would be equally – if not better – served by the S400 hybrid. Seeing as I’ve been something of a hybrid cynic in the past, that’s saying something.

Calm down, calm down... Give me the tech story, first

The new Merc S400 Hybrid uses the 3.5-litre V6 petrol that’s familiar from the C-, E- and S-class 350s. The units aren’t straight swaps, however, the 400 receiving revised cylinder heads, pistons, camshafts and more as well as the hybrid gubbins.

The seven-speed auto gearbox is the same one used throughout the range, but the lithium-ion hybrid unit is neatly integrated with it. It’s a relatively compact installation that’s designed to last the life of the car, but it does add 75kg over the non-hybrid petrol.

However, horsepower goes up, the hybrid adding a 20bhp hit to the 275bhp engine, and serving up an impressive 118lb ft from standstill. That helps combat the weight gain, plus lower C02 emissions by 21% compared with the regular petrol S350 – and it deliver 8mpg more.

Best of all, the mpg and C02 compare very favourably with the diesel, the hybrid turning in 35.8mpg to the diesel’s 37.2mpg and churning out just 186g/km versus the diesel’s 199g/km. And that, points out Mercedes, is cleaner and more frugal than the big – and, don’t forget, more powerful, larger-lunged – Lexus.

Okay, what’s the catch with Merc's hybrid?

Only the price: at €85,000 it’s around €12k more expensive than the diesel. But the exciting thing is what this promises for the future. There are no real drawbacks with the S400 Hybrid. Boot space remains the same because there’s no battery under the floor, and the driving experience feels just like any other petrol S-class with a stop/start system.

And because it’s a modular, easy-to-package hybrid unit, that means there’s no reason why every next-gen S-class couldn’t be a hybrid. With that come economies of scale, so the price would come down and – bingo! – hybrids for everyone. It's going to happen, believe us.

How does the Merc S400 Hybrid drive?

The S400 is so quiet that you barely notice the petrol motor cut out at the traffic lights, and under acceleration it emits barely a whisper where the diesel gurgles – adding to the impression that you’re driving a clean, green car. What’s more, you’ll never know that a gentle brush of the brake pedal doesn’t actually involve pads clamping discs. Instead, the engine is braked and the wasted energy transferred direct to the hybrid unit, Formula One KERS-style.

At just over two tonnes, the V6 lump has got its work cut out, yet the S400 never feels sluggish and proved a perfect partner at high autobahn speeds.

However, the S-class has always been a car to experience from the passenger seat or rear bench. To drive it enthusiastically is to experience the essence of waterbed on wheels with its slushy auto, wallowy suspension and feel-free steering. No, it's best to sample the serene ride, cutting-edge tech and beautifully supple seats from a passenger pew without the steering wheel, safe in the knowledge that the hybrid badge will deflect any G20 protestors as you disembark.


The S400 Hybrid is a genuinely good car and one that really does move the hybrid game on. The only pity is that it’s not coming to the UK, but that situation is bound to change when Mercedes unveils the next model over the coming few years. We certainly hope so.

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Price when new: £76,750
On sale in the UK: In the UK never
Engine: 3498cc V6 24v, 295bhp, 284lb ft
Transmission: Seven-speed auto, rear-wheel drive
Performance: 7.2sec 0-62mph, 155mph, 35.8mpg, 186g/km
Weight / material: 2030kg/steel
Dimensions (length/width/height in mm): 5076/1871/1473


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By Ben Barry

Contributing editor, sideways merchant, tyre disintegrator