GET set for a Subaru invasion - the firm's first diesel-engined car arrives here this month and it will mean fireworks in the fleet market.

For company number-crunchers will love the fact that the four-wheel drive Legacy Sports Tourer and Outback models, both estates, not only have the best fuel efficiency in the 4x4 car class, but also beat all main 2.0 litre two-wheel-drive diesel rivals, including the new Ford Mondeo and VW Passat.

Subaru's mid-sized estates will sell from £19,995 for the Legacy Sports Tourer 2.0TD R, which returns 49.6mpg on the combined fuel cycle, with exhaust emissions at 151g/km of CO2. The two-wheel drive Ford Mondeo estate equivalent returns 47.9mpg with 156g/km emissions, while the VW Passat 2.0 TDI estate has an overall 47.1mpg and emits 158g/km. Subaru's first diesel engine was developed entirely in-house, on the back of more than 40 years' experience with boxer, or flat, engine technology.

Flat engine configuration means opposing pistons can balance out each others' vibrations, giving a smoother power delivery when compared with V-layout, or in-line, engines.

Every Subaru car runs on a boxer engine, but the development of the new 147bhp 2.0-litre diesel is really big news for the Japanese firm.

This new engine will initially only be fitted to European-market cars, with the yet-to-be-introduced new Forester receiving the engine in September, and the new Impreza three months later.

When the initial rush for Legacy Sports Tourer and Outback models dies down, Subaru says saloon versions may follow once supplies become more plentiful. The diesel launch versions will come with xenon headlamps with pop-out washers, electrically-folding door mirrors, front projector foglamps, CD player with MP3 facility, dual-zone climate control with rear outlets and cruise control.

Safety equipment is excellent, and buyers are guaranteed the renowned Subaru ride and handling experience, developed from Banbury-based Prodrive's success in the World Rally Championship arena.

Helping protect passengers are the standard active front head-restraints, dual-stage front airbags, head and chest-protecting side airbags, curtain airbags, and anti-lock brakes with electronic force distribution.

Top speed for the Legacy 2.0TD R Sports Tourer is 126mph with a 0-60 mph time of 8.5 seconds, while the Outback's figures are only slightly behind at 124mph and 8.8 seconds.

Will it succeed? Undoubtedly - the business-user world's big players will love it.

Refinement will prove a key point, too - the diesel engine is quieter out on the road than mainstream rivals.

The engine has liquid mounts, with the body benefiting from extra sound-proofing, while the five-speed manual gearbox has higher ratios to suit the diesel's stronger torque and lower engine speed.

And last word on the new models goes to Subaru UK's managing director Lawrence Good, who said: "The significance of this outstanding new boxer diesel engine to both sales opportunities and our dealer network cannot be underestimated.

"With a UK diesel market share now running at 40 per cent, this is the answer to many loyal, and potential, customers' future motoring needs."