Oct.11 (GMM/Inautonews.com) Uncertainty about the ‘development engine’ now running successfully at the works team is the reason Mercedes’ customers are not being offered the new specification.

That is the explanation of Toto Wolff, after drivers of customer teams Force India and Williams expressed some consternation that they are now a step behind their works Mercedes-powered rivals.

He explained: “The new engine that we have had since Monza is a development engine. We wanted to try a different direction for 2016. But we are not yet certain about it,” said Wolff.

“So to do this exercise at all, we had to limit the production — when we had a problem with Nico (Rosberg’s engine) we were not even sure if we would have enough spare parts,” the Austrian is quoted by Speed Week.

Wolff, Mercedes’ team chief, argued that the new spec is not necessarily better in outright performance, “Even if people are saying that it definitely has more power”.

“That’s not the point,” he insisted. “For us, it is only a possible development direction for 2016.”

A more immediate concern for Wolff is the prospect of wrapping up Mercedes’ second consecutive constructors’ world championship on Sunday, which will happen in Sochi if the team scores 3 points more than Ferrari.

He admitted that the celebratory t-shirts are already printed.

“I can hardly say we have nothing ready if suddenly we are walking around in them,” Wolff grinned.

“But I’m not talking too much about it because I always imagine that this is a bad omen. So I knock on wood.”

In truth, Mercedes’ staff are probably less concerned about the celebratory t-shirts than they are about the prospect of a multi-thousand euro title bonus apiece.

“It’s the same as last year,” Wolff admitted.

“What we have managed to do this year in producing a dominant package again is incredible. And whether it was Malaysia or Singapore, we have always reacted well to the problems and defeats, which is something I’m very proud of.”