The Mazda6 MPS is much faster and more accomplished than its looks suggest. It is a high-performance turbocharged four-wheel-drive sports saloon disguised as a salesman’s car.

There was once a fashion for such “wolf in sheep’s clothing” machines, but nowadays if you’ve got it you want to flaunt it: witness the Subaru Impreza WRX STi and Mitsubishi Evo, which make no attempt to hide their sporting credentials.

Even the name is understated: in Japan and America this is called Mazdaspeed, but here it is MPS, for Mazda Performance Series.

Mazda invites us to compare the 6 MPS with refined but powerful Audis and BMWs and says that its most direct rival is the Subaru Legacy spec B, a sober £26,500 saloon. Another opponent could be the Ford Mondeo ST220, but Mazda doesn’t talk about the products of its parent company.

Perhaps this is missing the point. The Mazda6 was the first of the new generation of cars that has revived the fortunes of Ford’s Japanese business since 2002. It is nearly half way through its life cycle and Mazda wanted to add some excitement to the facelifted range that will appear later this year. It also wanted to point up its technical expertise without joining the circus of rallying or racing.

So the 6 MPS has a unique version of the Mazda four-cylinder engine that is now used throughout the Ford world (including in the Mondeo and the new Focus). It has direct petrol injection and a turbocharger, a combination that can produce excellent power and torque and eager throttle response with negligible “turbo lag” — as the similar engine in the new VW Golf GTI has demonstrated. The 2.3 litre engine in the Mazda6 MPS produces 256bhp, which propels this five-seat, four-door saloon to 150mph and from 0-62mph in 6.6sec.

The Active Torque Split all-wheel-drive system is directed electronically, switching automatically between three modes — normal, sports and snow — depending on how you are driving and how much slip it detects from the tyres. At low speeds on dry roads it is front-wheel drive only, but when going faster the computer varies the amount of engine output sent to the rear wheels, up to a maximum of 50%.

Hustled along a winding road, you can feel the four-wheel-drive system working to your advantage. A session on the TI Aida racetrack in Japan proved that the sports mode allows the enthusiastic driver to slide the rear of the car just a little while maintaining an impressively high level of cornering grip overall.

The Mazda6 is available as a saloon, hatchback or estate but the MPS version is four-door only. That is because the saloon bodyshell best lends itself to reinforcement to make a 50% stiffer platform and get the most from the suspension — which has double wishbones at the front and a multilink system at the rear, in contrast to the cheaper struts used by most rivals.

Although it is firmer than other Mazda6s, the MPS is gentler and gives a more comfortable ride than the rally-bred Subarus and Mitsubishis. The steering, unchanged from the standard car, is accurate and communicative and the brakes are enlarged to cope with the extra performance. The new six-speed manual gearbox is sweet and easy. There is no automatic option.

The interior is changed only in details: the standard car’s cheap-looking fake aluminium fascia centre is replaced by a “technical finish” (a superior grade of plastic), the steering wheel has a leather rim, and the seats offer more side support.

Outside, quite a lot is new, but you wouldn’t know it. Wider wheelarches enclose 18in wheels, there are subtle sill extensions, the lights have changed, and the air intakes and front bumper are deeper.

The bonnet is also curiously high. Mazda designers were so anxious to avoid the wings, spoilers and scoops of the Impreza and Evo that they funnel air to the engine’s intercooler through a duct hidden within the double-skinned bonnet. You are not supposed to notice that.

There is no doubt the 6 MPS is the best-performing and best-handling saloon that Mazda has ever made. When it arrives here in the summer — priced at around £25,000 — it promises to be an enjoyable companion, nearly as quick as those fierce rally specials and much easier to live with. But that’s a private affair: in the office or golf club car park, no one else will give it a second look.

VITAL STATISTICS

Model Mazda6 MPS
Engine type Four-cylinder, 2261cc, turbo
Power/torque 256bhp @ 5500rpm / 280 lb ft @ 3000rpm
Transmission Six-speed manual, four-wheel drive
Fuel/CO2 27.6mpg (combined) / 243g/km
Performance 0-62mph: 6.6sec / Top speed 150mph
Price £25,000 (approx)
Verdict A fast and capable sports saloon that doesn't look like one
Rating 3/5

THE OPPOSITION

Model Subaru Legacy 3.0R spec B, £26,500
For Direct equivalent for the 6 MPS in Japan. Six-cylinder engine, four-wheel drive
Against Similarly understated performance car, dull looks and interior

Model Jaguar X-type 3.0 V6 SE, £27,970
For Classier presentation, Jaguar style, reassuring four-wheel drive
Against Not as powerful, nor as fast or agile as the Mazda