Renault bring upgraded engines to US GP - but will Red Bull use them?

Renault will deliver upgraded engines for this weekend's US GP - but it remains to be seen whether customer teams Red Bull and Toro Rosso elect to use the new units.

The French manufacturers have run the same engine specification throughout 2015 but have now elected to spend 11 of their remaining 12 tokens.

"We will have our new specification of power unit available to use in Austin," said Renault's director of operations Remi Taffin.

"The principal changes involve the internals of the ICE (internal combustion engine) to give improved power and efficiency.

"We know that introducing the new PU will incur a grid penalty [for exceeding the season's allocation] so the decision to use will be made in full consultation with the teams."

Red Bull have previously indicated that they would be reluctant to use Renault's new engines unless they were convinced that the upgrade would deliver a big enough benefit to compensate for the grid penalty that would be automatically meted out against their cars once the new units are fitted.

But at the time Red Bull were speaking as they prepared to divorce Renault, their long-time engine partners. The landscape has shifted dramatically in the last month, however, with Ferrari and Mercedes rejecting their request for engines - leaving reconciliation with Renault the former world champions' only realistic hope of staying in F1.

In the circumstances, Red Bull's willingness - or not, as the case may be - to use Renault's upgraded engines may well provide a clear indication of where the team believe their future rests.

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