I think there was just a flurry of noise from the McLaren garage.....
For those asking, Vettel's headline time was set on mediums.
@RavithejaKammela: Honda announced last year they had copied the Mercedes split turbo design.
Ron Dennis has just told the media McLaren's problems today stem from "intense packaging inside the engine" - in other words, sensors aren't talking correctly to their counterparts.
Rosberg heads out AGAIN. Ericsson is out there too.
@AaronNoronha: Apologies if your comment has not shown up. We get so many comments through and it's only me or Laurence on at one time so sometimes comments slip through the net.
@MikeSpeed: That's always the way of F1 - it's all about interpreting the rules in different ways and trying to find the most innovative and competitive design. Something which makes F1 so unique from IndyCar, for example, or any other series which uses a standardised chassic.
@Prajesh: Twenty minutes left now.
@deepu: There's still time for a quick run so let's wait and see.
@vinayak: He's just set another quicker lap, too. For obvious reasons the teams don't tell us much about these runs because they are for their own internal use, but clearly that's the direction Ferrari is focusing on today.
Vettel's benchmark is down to a 1:22.620.
@Mark: It was a sensory issue which will be down to the tightly-packaged Honda power unit.
Rosberg just finished lap number 149.....
Vettel completes lap 50 as Rosberg finishes lap 150.
@lachu: I would say McLaren-Honda, it looks incredibly packed at the back.
Just back from a quick media briefing with Adrian Newey. The Red Bull had a battery issue in the morning which caused a brake problem and then another engine related issue.
Seems the Renault power unit will still be the thorn in Red Bull's side this year.
And Newey took the opportunity to have a dig at the regulations too, saying they were too biased in favour of the power units over chassis.
The chequered flag is out. Vettel's time at the top remains the fastest of the day. Ericcson holds second place ahead of Rosberg. Updated times and lap counts to come...
Thanks for joining us for today's practice session. We will be back tomorrow with more live commentary as well as news this evening. Lots of people are talking to the media later - including Fernando Alonso, Sebastian Vettel, Lewis Hamilton and Nico Rosberg - so keep checking ESPNF1.com to hear what they had to say.