Reliability issues with the new power unit "have been foremost among the complaints the team has had," but Renault has "hit back" and said that one of the underlying reasons for strained relations and poor performance "is that the squad isn't living up to its end of an arrangement to work as a de facto works team."
Renault Sport F1 Managing Dir Cyril Abiteboul: "It's one thing to state that Red Bull is our team and a works team of Renault, but it's another to make it happen." Abiteboul explained that "not being a single operation means that unlike teams like Mercedes and Ferrari, Renault and Red Bull lack an integrated budget with which they can plan ahead with and properly apportion between chassis, engine and driver development."
He said, "When there is an arms race in engine technology and the return on money spent is higher on the engine than it is going to be on a front wing then you have to review the whole economic view."
But Abiteboul said that he did not "want to play the blame game and admitted that Renault were also not where they wanted to be in terms of engine performance and reliability so far in 2015." F1i.com