Red Bull encouraged by practice form

But the team has yet to decide whether it will keep its F-duct - which it tried again in practice - on for the rest of the weekend.

Valencia was thought likely to suit McLaren in particular better than Red Bull, but Vettel and Webber ended Friday in second and third places, just behind pacesetter Fernando Alonso's Ferrari.

"Overall a good day, we did a lot of laps, we didn't have any problem with the car so we could follow our programme like it should be on a Friday," said Vettel.

"We need to see if we keep the F-duct in the car, we need to confirm that, but all in all I think the pace was promising today considering this shouldn't be our strongest track. We did a step forward with the whole car - it was a good day for us."

Webber agreed that it had been a promising start.

"We had a good Friday programme with no interruptions and evaluated the tyres and the F-duct which we will look into tonight - as we all know it's not without its challenges getting that thing working," he said.

"The track changed a lot this afternoon, the conditions were moving around a bit. But a very productive day for us: the car ran faultlessly and was pretty comfortable so looking forward to tomorrow."