The new D-segment Ford Mondeo is too big for Mazda, especially in Japan, which is why the Japanese firm did not share the platform for its redesigned 6.

Platform sharing is seen as one of key ways for the car industry to achieve economies of scale and cut costs and, in the Ford empire, this means the small car B platform is shared by the Mazda 2 and new Fiesta, which will be launched at the Geneva motor show next week.

The Focus, Mazda 3 and Volvo S40/V50 share the larger 'C' platform. Logically, the 6 should share its platform with the new Mondeo.

But it doesn't, according to 6 programme manager Ryuichi Umeshita.

"First of all, we had very good feedback from the previous generation 6 so it was natural for us to continue with that platform. "Secondly, new Mondeo is too big for us, especially in Japan."

So big, in fact, that it would have problems fitting into Japan's popular automatic parking bays, and it's wide enough to take it into a higher tax band.

Umeshita admits that "sharing platforms is an assumption we have to make" but there can be additional costs involved in having to re-engineer assembly facilities. Sometimes it can be more efficient to develop an existing platform because it will fit into existing assembly and painting facilities.

That said, there is very little in terms of parts carried over from old 6 to new model. "The only commonality is some engines and some transmissions," said Umeshita who has worked on 6 programmes in Japan and the US for the last nine years.

Even the engine firewall has been changed and the suspension is new with new fixing points. "We wanted new suspension to give us more precise steering," he said.

The idea of sharing isn't just confined to physical parts. "We respect Ford's technology and we have learnt a lot from them and there is a lot of knowledge sharing especially on the engineering side."

Much is shared between the B and C platform models of Ford and Mazda. "We have very good commonality and a very good relationship on those models. I'm not sure if we should go further - there is no big requirement to share more."

Umeshita confirmed that Mazda's core B, C and D segment models would continue for at least one more generation but there would be no high performance MPS version of this new 6.

"I'm carefully watching the market reaction to that decision but I'm also considering the CO2 implications. It would make more sense to have a high-powered diesel engine."