IT is the limousine that's as economical to drive as a supermini and it's taking fuel saving technology to new levels.
The new Mercedes S 300 hybrid combines a diesel engine with an electric motor to deliver a claimed 61.4mpg.
That's in the same league as a one-litre Ford Fiesta yet the Mercedes is a two-tonne luxury liner that is more than 17 feet long.
Dubbed by many as the finest car in the world, the new hybrid makes the S-Class even more credible.
With emissions of 120g/km it is the most eco friendly large executive car on the market and a compelling choice for chauffeurs, professional drivers and company bosses.
Priced from £72,260 the diesel hybrid is some £5,000 more than the diesel only S 350 but with its lower emissions has significant tax advantages.
For company car purposes the benefit in kind index is 20 per cent - five per cent lower than that of the diesel and if you buy privately there's no road tax in the first year and £30 a year thereafter.
In this class of car hybrids are nothing new but diesel hybrids are still rare beasts.
Mercedes already has a petrol hybrid in the S-Class line up which tips the scales at £74,685 but with a claimed 44.8mpg and emissions of 147g/km is not nearly as efficient.
The diesel hybrid hits the mark in no uncertain terms and the beauty of the Mercedes' system is that it operates so unobtrusively.
The car we sampled was a long wheelbase S 300 BlueTEC Hybrid in AMG Line trim which with extras cost £80,415.
Much of that was down to the £4,335 executive rear seat package which included reclining seats, roller blinds and individual climate control.
Absolute luxury in the back of the S-Class is complimented up front with high tech displays which show how the hybrid system is operating through a number of high definition graphics.
On the instrument panel part of the rev counter indicates whether the car is charging or using battery power while the amount of charge in the electric system is shown in percentage terms - as is the fuel remaining.
There are eco and sport modes to go to the extremes of what the S 300 has to offer but leave it to its own devices and the results are quite incredible.
On a drive through the suburbs of London then out on to motorway and dual carriageway the S 300 averaged 47.8mpg over more than 50 miles and there is nothing lacking in performance.
Like all versions of the S-Class the top speed is restricted to 155mph and while the diesel hybrid may not be quite as quick as the other versions it can still accelerate from 0 to 60 in 7.6 seconds.
In traffic more often than not it will run on battery power while lift off the throttle at motorway speeds and the car will switch into a coasting mode to conserve fuel.
With air suspension the ride is sublime while the noise insulation allows for almost silent running.
The S 300 hybrid features a 2.1-litre four cylinder diesel engine mated to an electric motor which is housed in the eight speed automatic transmission. The combined power output is 231 bhp and with additional torque from the electric motor the mid-range acceleration can be very rapid if required.
Boot space remains capacious at 510 litres with the battery pack housed below the car in such a way that it does not impinge although the hybrid does weigh slightly more than the diesel version.
Theoretically the S 300 hybrid has a range of 950 miles with a 15.5 gallon fuel tank making it a formidable long distance performer.
As with any other S-Class it is crammed with sophistication and as the flagship Mercedes saloon it has world beating features such as cameras which scan the road ahead and adjust the suspension to iron out bumps.
It is also the first car without a single light bulb and has a complete LED set up for everything from the headlamps to the vanity mirror illumination.
In the corporate world the S-Class has always been regarded as one of the great status symbols but in its latest guise it is a game changer of the highest order.