Toto Wolff has explained that the current engine disparity between the Mercedes factory team and Williams is a matter of logistics, not intentional strategy.
The two Mercedes drivers Lewis Hamilton and Nico Rosberg are benefiting from a newer specification of the manufacturer's power unit than its leading customer team, but Wolff insisted this week that this hadn't been done intentionally in order to give the works team a competitive advantage on track.
The FIA announced this week that it will not be allowing manufactuers to offer older specification power units to customer teams in 2016, with Article 23.5 of next year's regulations stating: "Only power units which are identical to the power unit that has been homologated by the FIA ... may be used at an Event during the 2016-2020 Championship seasons."
"The engine is very much a research and development engine," the head of motorsport at Mercedes explained of the current situation that had arisen in 2015 with different engine specifications being available to Mercedes than to Williams.
"We decided on trying out the direction that we believe could be beneficial for next year, but we are not 100 per cent sure."
The team had a problem with its initial roll-out of the updated unit in Rosberg's car at Monza when it suffered problems during free practice. Rosberg was forced to switch to a used engine that already had a lot of miles on it and which failed during the Italian Grand Prix.
That was a big blow the German driver's hopes of competing with his team mate for the championship, but Hamilton himself retired from the following event at Singapore with more Mercedes power unit issues.
"When we had the problem with Nico’s engine we weren’t even sure we had the spare parts to give him another engine," said Wolff.
"In order to do that exercise you can only concentrate part wise and logistically on the two engines."
As for Williams's current situation with regard to the latest engine update: "We just can’t supply it logistically."
Wolff also explained that at this stage the new power unit wasn't necessarily even offering any significant performance advantage over the existing one already being supplied to Williams.
"From phase three to phase four, the main thing it is not a performance step up. Of course people always say that engine must be much better, but that is not the case.
"It is just a development direction for next year. We can probably run it a bit harder for a bit longer, but it is not the miracle step up."
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