Mercedes-Benz S-Class S400d review: the ultimate airport taxi

A luxury car powered by diesel?! Who’s going to buy one of those?

Quite. And yet….

You’re going to tell me it’s really good.

I am, just not yet. Because diesel is a hard enough sell for people these days, before you even consider how backward the idea of a diesel luxury car sounds when alongside it you have an S580e hybrid with 60 miles of e-range and the far more forward-looking EQS luxury EV, both available for about the same amount of money.

So who would have the diesel?

You tell me. The best use case I can come up with is the long haul chauffeured executive who can work in the back between Frankfurt and Munich. Like it or not no petrol, not even a hybrid, can match diesel as a long range fuel yet. This claims 38.7mpg combined (and 196g/km CO2) but the reality is an easy 40mpg cruise. Which means a 670-mile range. You would have to debadge it. The ‘D’ badge is not a good look these days.

I see what you did there.

Airport taxis. Sorry, that was a bit random, but I can see airport taxi firms loving these, but then why would they bother when they’d have the cheaper S350d which starts at £81,650 where this bases from £94,135?

The price uplift is partly because the S400d is long wheelbase only, but I still can’t help thinking it represents good value. Loads of cars cost £100k these days, but relatively few of them seem to offer a load of car for the money. The diesel range flagship, despite being three model steps up, is only £10k more, so you’d have that. And never tell anyone what it’s called.

Why?

Because the full name lacks any semblance of elegance. Merc has played ‘Premium Car Wordwang Bingo!’ so the car you’re looking at here is the S 400d 4Matic L AMG Line Premium Plus Executive.

Well kitted out though, yeah?

It wants for absolutely nothing. Here’s the stuff I played with and noticed. The matrix pattern LED lights are the best I’ve ever used. There’s a 3D driver display, it’s subtle enough to elevate the dashboard without being distracting. The Burmester sound system isn’t quite up to Bentley’s Naim audio, but it’s plenty good enough. I hate head-up displays. I didn’t hate this one, and it put more information in the screen than any other I’ve ever used. The passenger seat can contort itself into the footwell at the press of a button. It’s amusing to watch. The ambient lighting is gorgeous. And playful.

How can ambient lighting be playful?

Because it responds to you. The Mercedes Me voice control has now advanced to a point where it can work out which seat the orders are being barked from. So I sat in the back and ordered it to increase the temperature (couldn’t possibly lean forward, I’d reclined the chair as far as it would go). Not only did it get the instruction right – and just for that one climate zone, not the others – but the ambient lighting temporarily glows red. The lighting also dances as the voice speaks to you. It’s daft and shouldn’t be important, but helps give this new S-Class more human characteristics. It’s also worth pointing out that this car didn’t have a single option fitted – everything was standard.

What about space, quality and ambience?

I literally couldn’t pick a fault with any of it. A long S-Class is over 5.3 metres from stem to stern. The boot is huge, the rear is palatial, it feels luxurious in a way that neither the Audi A8 nor BMW 7 Series do. It’s more artful and creative than them.

What about the driving environment?

There’s a lot to master. The central screen interface is very good, the graphics are lovely and the screen buttons mostly big enough to press on the move, but this tendency to fit black panels with touch sensitive areas beneath them needs to stop. Merc is not the only guilty party – we see it across the VW Group as well – and it’s done to save money as you have one plastic panel rather than half a dozen individual buttons.

But a volume slider isn’t fit for purpose, the thumb patches on the steering wheel are awkwardly angled and hard to use, the door-mounted seat controls are now touch sensitive, so don’t physically move. It’s a shame because the ambience, the craftsmanship, the design and materials are just gorgeous.

What about the driving? How’s that diesel?

It starts silently, it barely rattles outside, it merely hums when extended, there’s almost no vibrations. I’d say it’s as smooth and possibly more refined than the V6 petrol Bentley fits in the Flying Spur Hybrid I drove recently.

And it’s plenty rapid enough. It punts 2,090kg of German lux to 62mph in 5.4secs. In reality you never drive like that and tend not to coo about the mid-range muscle either. Because you’re almost never aware of what gear you’re in. The drivetrain integration is peerless: you operate the throttle, the car faultlessly interprets that. The end. It makes it very easy and relaxing to drive.

Does the ride match that?

I’m not sure I’ve ever driven a car with better body control. Or rather more suitable body control. Yes, it has the full suite of hidden helpers, right down to Crosswind Assist, but the way the car translates your inputs through its processors is remarkable.

Because it’s not just when you’re trying to drive smoothly that the S-Class is so effortlessly relaxing, level and calm, but when you drive like you're caught in a Hollywood chase scene too. You throw it around, make your inputs deliberately harsh, but what you get back remains silken. It’s like Merc has realised the weak link is the clumsy driver and they’ve worked out how to buff their edges off and make them look good.

It flows better down a road than it has any right to. Does it quicker than you’ll believe possible, and actually gives the driver something in return. Mainly shock and surprise that the car is clearly better than he is.

Does the S-Class still have a role to play?

Interesting question, because I didn’t think it would have. I thought Merc would have got distracted by the EQS (which is the same money as this, just slightly less chauffeur-y), seen that as the future and gone through the motions with the S-Class to satisfy the dwindling audience for a conventional luxury car. Not a bit of it. This continues to be the industry benchmark for luxury-saloons-that-someone-else-drives.

Why not luxury saloons in general?

Because if you drive one of these yourself, even if it’s a short wheelbase version, you look like a professional driver. No German luxury car sends out the right signals. Especially not one powered by diesel.