Iain Dooley, PA senior motoring writer, is all fired up about the new down-sized four-cylinder diesel in the Mercedes-Banz CLS.

Downsizing is all the rage these days – even in the premium sector. It used to be the case that a car's status was inextricably linked to what was under the bonnet. The bigger, the better and all that.

With a greater focus on fuel economy and lowering emissions, that's no longer the case. And with the recent advances in engine technology – better engine management systems, more powerful turbo and superchargers – less is sometimes more.

Mercedes certainly hopes so with its four-cylinder diesel CLS. The car itself is something of a statement of intent – if you want to make your neighbours or work colleagues jealous, get a CLS. This self-styled four-door coupe-like premium model's appeal has centred on its looks. It might share much with the more sensible E-Class under the skin, but it looks a darn sight more sexy with its rakish looks and sweeping profile.

But it's always been sold with a brace of six and eight-cylinder engines, as that's what you do when you're selling a premium product. However, in a bid to broaden the second-generation car's appeal, Mercedes has dropped a 2.2-litre four-cylinder diesel in the nose. The cynics will view this as Mercedes selling out and devaluing the car but it's clear once you turn the key that compromise is nowhere to be seen.

With 201 horsepower and power to the rear wheels through a smooth seven-speed automatic gearbox, down-sizers will warm to the car's performance potential while 54.3mpg and 135g/km of carbon dioxide emissions should appeal to both fleet managers and company car-driving executives alike.

And it's here that Mercedes hopes to score with the CLS. Why have an E-Class when you can now afford to run a similarly-powered CLS? That noise you hear is men in suits rushing to their local Mercedes dealership to place orders.

Granted, the car's appeal is a little more complex – being a strict four-seater the CLS isn't going to suit everyone's lifestyle. For the company executive, empty-nesters and those with a grown-up family the CLS makes a lot of sense. It's practical enough thanks to good levels of cabin storage and a capacious saloon-like boot. It's plush interior probably won't be able to resist the advances of a sticky-fingered toddlers, but that's who people-carriers were invented for.

The CLS is for people seeking to make a style statement and move away from the traditional three-box saloon. They probably want to retain most of that car's practical features, and the big, sleek Mercedes does a good job of combining the best of both worlds.

In 250 CDI trim it also does a good job of disguising the fact that it's powered by 'only' four cylinders. The gruffness associated with most four-pot diesels is refreshingly absent from the CLS, and thanks to a decent slug of torque the car is no slouch around town and it's at its best maintaining a brisk pace on the motorway. It's times like this that you'd be forgiven for viewing the more powerful 350 CDI variant as an extravagant purchase.

Add Mercedes' widely-acclaimed seven-speed automatic gearbox and a weighty steering and you've got the makings of a driver-centric experience, but one that hasn't forgotten the needs of the other occupants – comfort and refinement is right up there with cars costing considerably more.

The media love to pigeonhole cars and, much to Mercedes' delight, the first-generation CLS was a tough car to categorise. Even now it's not your average premium car and, on paper, it shouldn't really make sense – when exactly does a four-door coupe make sense?

With the CLS Mercedes has managed to pull the proverbial rabbit out of the hat. It makes sense every time you look at it and drive it. And with the inclusion of a frugal yet willing four-cylinder diesel engine, it's now also a serious business machine for executives who value the finer things in life.