F1 Spanish GP: Red Bull demands Renault focuses on performance

Renault has endured a disastrous start to the 2015 campaign, and Red Bull driver Daniel Ricciardo is already onto the final engine of his permitted allocation, meaning grid penalties for going over that limit are inevitable later in the year.

Ricciardo's Spanish Grand Prix weekend was compromised by Red Bull trying to limit his engine mileage during practice, but Horner feels that Renault should shift its focus from reliability to chasing performance for the rest of this season.

"It's positive that Renault have got four engines to the finish without any white smoke," said Horner after the Barcelona race, where both Red Bulls were lapped.

"The focus desperately needs to turn to performance before too long. Renault have got things in the pipeline but it's all a work in progress.

"Obviously they are nervous about reliability so I think it will be the second half of the year before we see anything significant.

"We're so far on the back foot with reliability anyway that this year is pretty much a write-off, and you've just got to go for it even if you end up using 20 engines.

"It would be better to learn and make progress in preparation for next year than be conservative.

"It's far easier to make a fast car or a fast engine reliable than it is a reliable car fast. Our philosophy has always been to push performance."

Horner believes, however, that rather than simply holding back performance gains, Renault is yet to work out the best way to get more speed from its power unit.

"They know what the deficit is, the question is how are they going to make that up and that's the bit they don't know at the moment," he said.

"They are looking at different solutions but they haven't got a definitive direction yet.

"But hopefully they are homing in on that and of course things in the engine world seem to take an awful lot longer than in the chassis world."