Mercedes has "a few balls in the air" as it balances precarious PU situation

Toto Wolff has revealed Mercedes currently has "a few balls in the air" as it balances a tricky situation regarding its power units.

Lewis Hamilton is down to his final two systems for the year which he has conceded are being nursed at present in a bid to make it through to the end of the F1 season without taking a costly grid penalty.

Team-mate Valtteri Bottas has now taken five power units this season, including two in the last two races in Italy and Russia, with the one used in Monza "gone" according to the Finn, although the team has insisted it is being assessed.

Wolff knows Mercedes face a thorny dilemma regarding future changes, notably whether Hamilton's W12 will require a new PU and with it penalties that would impact his title challenge.

Explaining Bottas' switch in Russia and the plans for the rest of the season, Wolff said: "We haven't only made a precautionary engine change because we felt we want to stockpile.

"But because we want to understand the engine's performance and that has given us some question marks.

"At the moment we take one race weekend at a time and reassess the performance of the power units and then take decisions. We haven't decided which engines will go back into the pool."

The issues affecting Mercedes this season have not only been confined to the works teams but also partners Aston Martin and Williams, and to a lesser extent, McLaren.

With power units due to be homologated from next season for a period of four to five years, Wolff concedes the remainder of the season is vital to understand the system and ensure its performance is optimal going forward.

"That's why we have a few balls in the air," said Wolff. "You need to have the right balance between making sure you really sort out all the gremlins that you have with a power unit, not only for this year but also next year's power unit.

"Definitely we are in a phase of assessment on how to continue this season in terms of power units."

Wolff has said it is "a possibility" a PU change in Hamilton's car could take place this weekend in Turkey, although any firm call has not been made.

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