Every car company faces environmental pressure, but not many have responded with the splendidly single-minded determination of Subaru.

Because when the new Impreza is unveiled at Frankfurt’s motor show in September, its brand-spanking, flat-four diesel engine will be a key feature, yet Subaru expects to make not a penny of profit from this much-needed new technology. Hard to believe, I know, but a senior executive at Subaru’s UK importer confided this fascinating snippet, apparently repeating what an exec in Japan said.

Maybe that comment was in jest, but with diesels taking about half of the European market and, in some countries and market segments, a much bigger proportion, it poses questions for Subaru’s long-term well-being.

Of course every car enthusiast can only applaud Subaru’s determination to go-it alone with the flat-four diesel, whose unique layout means that it can’t be sold or shared with any other car-maker.

Reputedly the design has been in development for 25 years, some of that time featuring the help of Toyota, and we know a few details, like the clever packaging of the intercooler below the engine that means it won’t force Subaru to spoil the bonnet line of the Impreza with a 1970s-era air intake. It also sits lower in the engine bay than today’s Impreza, which bodes well for road-holding, handling and turn-in.

Of course Subaru’s recent divorce from GM has helped force its hand into going it alone with the flat-four diesel, a move that’s also pushed Subaru into being a one-platform car-company.

Effectively the new Impreza is a short-wheelbase Legacy/Tribeca which means the introduction of a multi-link rear axle where previously there were struts. In that regard the Impreza matches up to Europe’s best, the Focus and Golf.

With global production of around 600,000 cars a year — which puts Subaru in the lower-middle ranking of the world’s car-makers — it can’t afford the diesel investment to drag it down. Saab, Porsche and Jag are 100k cars-a-year makers, hence their cost-volume conundrums, while the bulk of other established car-makers measure volume in millions.

The Impreza will hopefully address this shortfall. The new model is designed as a hatchback to broaden appeal and lift sales in Europe. In Japan, where hatchbacks sell in increasingly large numbers, it ought to do well too. Only for the US will there be a four-door sedan.

As if to reinforce that message, Subaru’s launch models at Frankfurt will have small capacity non-turbo engines – cooking models tasked with competing with the Focus, Golf, Megane et al. Not until Tokyo in October will the fire-breathing WRX STi models take a bow.

Let’s hope that the Impreza petrol-engined models get off to a good start at both these launches, because with all those diesel-engined models losing money for Subaru, profits have got to come from somewhere.