@grahamg: This engine formula is all about getting as much power from the fuel you have available - efficiency is the key. Upping power is only useful if it doesn't use too much fuel so the two are entirely interlinked. Then there is the Energy Recovery System, which recovers power from the fuel that is used via the rear axel and the exhaust. The best way to think about it is that the car has 100kg of fuel, which is potential energy, and it's all about getting the most power from that potential energy over the course of the race. Of course, if you can use less fuel the better as the car is also lighter - another factor in the very complicated equation.
@fdespotovski: We believe it is a split turbo similar to the Mercedes design.
It seems Raikkonen's 1:27.523 from earlier was disallowed for some reason (possibly a cut chicane). His best time at the moment is a 1:28.726.
@Marais: It's not yet clear how it will fit into the regulations. But I should imagine no-one will risk flouting the rule unless they get approval from the FIA.
@Force_Indian: I don't suppose he has to, but I imagine he will. Mercedes probably have a race suit ready as he is the reserve driver. I remember when Kimi was unwell two years ago for Lotus, Davide Valsecchi had to wear all Raikkonen's overalls and even his fireproof underwear. I don't think Kimi asked for it back...
@liv: One car shared between the two drivers. By this stage some teams might have a second chassis ready, but it's possible there is still only one of each car (test ready) in existence.
Here's all the news we have on Hamilton:
Button has just gone quickest with a 1:27.959. McLaren looking in much better shape here than they did in Jerez.
@LawrenceSm22: No news yet from Force India on their plans. Perez and Hulkenberg are due to drive later this week, but I'm not sure if they are at the circuit at the moment. However, because they are only using the 2014 car to evaluate the tyres they may opt not to run in the afternoon.
@CJK: I think Jerez was a perfect example of the times being a bit misleading. Hopefully Sauber will be challenging for the points again, but the car doesn't look like a big step on from last year from the outside. The updated Ferrari power unit will help, however.
Button's 1:27.959 has been cancelled, so Kimi goes back to the circuit. Button must have gone off somewhere on the circuit.
@CrM: Nope, either that or the Red Bull is so well camouflaged it's not registering its laps each time it crosses the line.
@forza: There was no pre-season test here last year but Maldonado set a 1:24.871 during the in-season test. In 2013 Rosberg set a 1:20.130 in the Mercedes W04 at this test.
Maldonado is finally back out after his earlier woes and has posted a much more representative time, a 1:29.949, moving him above Hamilton into sixth.
Nasr breaks into the 1:27s and goes fastest - but let's see if this one remains as Kimi and Button both had times erased earlier.
The latest on Hamilton is that he woke up with a fever this morning and only felt worse when he got in the car. Rosberg is at the track, but with a big run plan, Mercedes claims it does not want to overwork its drivers - Rosberg will be back in the car tomorrow. Wehrlein, meanwhile, gets a surprise chance to sample the W06 after expecting to spend a full day in the Force India.
@RashmilRajagopalan: They are mainly testing tyres. Both race drivers are in Spain this week and Perez is due to drive tomorrow. He will most likely be called on if they want a replacement.
@Red_ZA: Sadly it's last year's Force India, so not actually two current cars. But I can't think of a comparable example, no.
@SiegfreyCo: There is no limit, so it's usually as many as they need. Engine changes are quite lengthily procedures, so they don't chop and change during the day unless they have to.
@RacingFan: I think that you might be jumping to a few conclusions. Yes, McLaren is behind its rivals, but that's to be expected with a new power unit. They are ahead of where Red Bull were last year (and you could argue at a similar point to where they are this year) and the RB10 went on to finish on the podium (albeit later disqualified) in Australia and second in the championship by the end of the year. It's still early days.
@SurendranSelvaraj: The teams are allowed to use whatever they want. They request the tyres from Pirelli, although if they are hoping to achieve mileage the super-softs are fairly useless. There is also a special winter compound supplied by Pirelli which is better suited to these cold conditions.
@Srini: No, it's still the camou-Bull. I'll dig out a picture (there aren't many due to the lack of laps).