THE big Mercedes-Benz CLS is a car you buy with your heart because of its stylish, curvy four-seat luxury coupe approach to motoring.

But one version, the 250 CDI BlueEFFICIENCY is a car that you can also buy with your head.

This model proves beyond doubt that you don't have to have a six or eight cylinder engine to enjoy the world of upper-crust driving.

Under the bonnet lurks a four-cylinder diesel, which you might think is a bit wimpy for a car of this type, but this one works a bit a of magic that is very relevant to the economic and environmentally aware attitudes of today.

Bearing in mind that this engine is just 2,143cc in capacity, its capabilities are amazing with 150mph on tap, a 0-62mph sprint on 7.5 seconds and a CO2 emissions rating of just 135g/km.

But the star feature is that this quite massive Merc can return over 54.3mpg on the combined cycle.

A lot is owed to the latest Mercedes-Benz BlueEFFICIENCY technology which is not just aimed at economy but providing enough driving enjoyment to give a sugar coating to environmental considerations.

The cabin is sumptuous being purposely designed to accommodate four in typical Mercedes slightly understated luxury.

The central console stretches the full length of the cabin, dividing the space into four distinct seating locations. It is without doubt first class travel for all, and even the car's downswept rear roofline does not impede headroom in this amazing vehicle.

The new CLS is the latest interpretation of the Mercedes-Benz large coupe, a car which has been around for a while and created a stir when it came on the scene. Since then it has become an icon and in my view is a much smarter choice than the E-Class saloon.

First impressions count a lot with any car and I was immediately won over by the car's amazing electromechanical power steering which transmits a wonderful amount of road feel and helps to give this big car the feel of a taut sports saloon.

It might not be a full-blown sporty drive but there is just enough of that buzz to make this car exciting. The engine is astonishing and gives bags of thrust right through the power spectrum. It never seems to be working very hard and is a tribute to its designers.

Another feature which racks up the points is the 7G-TRONIC Plus seven-speed automatic gearbox operated by a column selector -a feature redolent of the days of classic luxury motoring.

This is one of the best transmissions of its type I have encountered and suited the four-cylinder diesel perfectly.

But as you might expect all of this does not come cheap, but at £43,360 you get a lot for your money.

Standard specification is, as you might expect sky high but as with most Mercs there is always a raft of options available.

The car I drove was loaded with them and they included a reversing camera at £390, surround sound at £650 a COMAND Online multi-media system at £950 and an intelligent light system at £895.

All in all a prime example of pure luxury with an eye to low running costs.