Few new cars bring something genuinely different to the market that rewrites the rules of the game. But the latest Mazda6 would appear to do just that.

The new engine technology has been well documented: Mazda has produced a diesel engine with a lower compression ratio than any other car on sale to improve efficiency, while achieving a similar outcome from a very high compression ratio on the petrol engines.

This, combined with a lighter and more efficient manual and automatic gearboxes, reduced weight in the chassis and body structure is the basis of the new technology Mazda has dubbed Skyactiv.

For the first time in the Mazda6, the fuel-saving features has been combined with a new energy regeneration technology called i-Eloop (see separate panel).

Mazda managing director Jeremy Thomson said the company had lost out with fleets over the last two years from not having a Mazda6 with competitively low CO2, and although it introduced the Business Line edition with a lower P11D value, fleet registrations fell away in favour of retail during 2011 and 2012.

“Being less competitive on CO2 emissions has been a particular challenge for us in the last few years, and out fleet sales with Mazda6 dropped off significantly.”

There is no single derivative of the Mazda6 on sale in the UK with CO2 emissions higher than 136 g/km. That includes saloon and Tourer, petrol and diesel, manual or automatic. The highest CO2 for diesel variants is 129g/km, with the best performing 108g/km available in 150bhp diesel saloons.

Although there is an increase in P11D value across the board company car tax and running costs are much lower. In fact, the 2.2D 150 Sport, which has a P11D value almost £7,000 higher than the outgoing 129bhp Business Line edition, has lower BIK tax.

Unlike the previous Mazda6, the new model will not be offered as a hatchback. Mazda says much of the D-Sector hatchback volume in the UK is driven by the popularity of the Ford Mondeo and Vauxhall Insignia. In its own customer research, Mazda says only 8% of people said they chose the hatchback bodystyle because of its versatility, with the rest suggesting it was a default choice.

The company says that for those who really want the versatility a hatchback provides over a saloon, dealers will try to persuade them that the CX-5 crossover would be a suitable alternative rather than losing the customer to Ford or Vauxhall.

In any case, with premium brands encroaching on the mainstream D-sector’s territory, saloons perhaps create the impression of a more premium feel in the UK.

While Mazda freely admits it can’t compete with the likes of Audi, BMW and Mercedes-Benz on brand image it feels it’s in with a good shout on running costs even when looking at cars at the top end of the range.

For example, the 2.2D 175 Sport gets close to the BMW 320d EfficientDynamics saloon for cost and tax liability, but add the extra equipment that Mazda has as standard and the costs and tax weigh heavily in the Mazda’s favour.

We drove a manual 2.2D Sport in proper UK production specification and as well as offering the best quality of any of the examples we’ve driven so far, it was also noticeably more refined, particularly compared with our first experience with an early pre-production car in September 2012.

Acceleration from the high-power diesel is rapid thanks to its class-leading 309lb-ft of torque and the six-speed manual gearshift that does its best to imitate the short-throw slick-shifting gate in the Mazda MX-5.

The diesel engine is all-aluminium and combined with Mazda’s sharp steering makes it a very enjoyable car to use for driving the long way home.

But most of these will spend the majority of their time on the motorway and the new Mazda6 is equally adept at that discipline of fleet life.

And even on the 19-inch wheels fitted as standard to the Sport, although the ride feels a little less settled on imperfect surfaces, it never feels uncomfortable.

The task ahead of the Mazda6 is a tough one in a sector that has been in steady decline for many years. But Mazda seems to have got virtually every ingredient right to ensure it will succeed.