Road Test: Mercedes-Benz S Class S350 CDi BlueTEC 4dr Auto

This is the new S-Class. If you're squinting at it to work out what's changed, we don't blame you. And we don't blame Mercedes for such a gentle facelift, either - the S has a reputation for pioneering new tech with every major development of the car and this one, now four years in production, needed only a tickle to stay ahead of the game.

Visually, that means a pointier grille, some LED lamps, a few subtle bumper mods and a couple of trim tweaks inside. Under the skin things get more interesting - Mercedes has added to its list of safety gadgets (stuff that'll inevitably trickle down onto ‘normal' cars in a few years) and a host of engine mods to make the S-Class a bit easier on the planet.

So let's start with the green bits. Engines across the range are virtually untouched, but an under-body aero package, low-resistance tyres and a system to disengage the auto 'box at standstill mean emissions are reduced. Figures for the diesel (Merc's best-seller in the UK) are down from 220g/km to 199 and fuel economy is up a bit to 37.2mpg.

We drove the S350 CDi, S500 and S600 models on our test and, to be honest, you'd be hard-pushed to notice any real difference from the outgoing versions, save perhaps from a slightly smoother idle thanks to that clever gearbox. And that, incidentally, re-engages when you lift off the brake pedal so there's no delay when you pull away.

There's an S400 hybrid, too, which adds battery power to the V6 petrol engine, but with the diesel such a strong seller and extra fuel savings marginal, we won't see it here.

Moving on to the safety stuff, there's a host of kit that litters the S-Class brochure with the word ‘Assist'. Adaptive High Beam Assist stops you dazzling other drivers, Attention Assist barks at you if you doze off (it watches your body movements to decide whether you have or not) and Lane Keeping Assist sends vibrations through the 'wheel if you unintentionally wander across the road.

Perhaps most interesting - and baffling - is the introduction of a crosswind stabilisation function to the stability control. It detects the gust and effectively loads up springs on opposing corners of the car to counter-steer into the wind. We tried it out using a wind machine at the Merc test facility in Stuttgart and it's startlingly effective - you feel a tiny nudge as the car senses the rush of air but then you are eerily returned to your original course.

So, a scrub up on the outside and a sprinkling of extra tech to remind the other luxury car makers of their place in the world. Like we said, you can't fault the logic in that.