Good morning and welcome to ESPN's live coverage of the fourth and final day of the final winter test of the 2015 season!
It's a bit overcast here at the Circuit de Catalunya this morning and we've had a slight splattering of drizzle to get us started.
Apologies - I forgot Mr Vettel for my original line-up. Sundays, hey?
I can assure you he is driving today! List amended now.
Temperature is 8 degrees Celsius today. Track temp currently just over 11.
The session is under way and we have four cars out on track - Nasr, Rosberg, Vettel and Bottas.
@AnsharLaw: They have, but even race sims are hard to accurately compare due to differing conditions on each day etc. I think Mercedes looks the strongest once again, that much is obvious. Ferrari seems to have improved but we won't really know until we see some qualifying simulations today where it stands in terms of raw one-lap pace.
@JanVisser: Yep. We spoke to Eric Boullier yesterday and he said the team was weighing up whether to do a race simulation today.
Perez's helmet looks a bit funky this year.
@AnsharLaw: I was thinking the same thing!
@JanVisser: Sure. We'll be doing a more in-depth analysis of each team over the next week - so you have that to look forward to :)
As a quick summary though, I think Williams seems quietly very happy with how its managed to tick things off this winter. Sauber and Toro Rosso have also been quietly accumulating a lot of laps and that's a good sign for them. Ferrari is hard to gauge, as they are the most secretive team of the lot, while Red Bull's winter has been pretty low key all round. But then that's better than the high profile winter it had last year....
Vettel is the first man to post anything near a representative time as he crosses in 1:29.863.
@rockedin123: It was down on the times of Mercedes' race simulation but I was impressed with the consistency of Raikkonen's final stint - albeit until he lost the tyres in the final few laps. As ever with testing it's difficult to really make an accurate reading, plus we're in the business of reporting facts not speculating - though some journalists are much more comfortable doing the latter.
@Fritz: I don't think they're going blind folded at all. Testing is important because it gives teams the chance to iron out these issues early and McLaren is learning a lot every day. A race simulation is slightly high risk as there's more chance of breaking down and McLaren needs to utilise every lap it can today.
Rosberg goes purple in the first two sectors ad then jumps top of the timing screens, a 1:25.678 the new benchmark.
@ankur: It's a combination of both, I think. Pirelli promised a big step forward with these tyres this year but these cars are getting faster and faster all the time. It won't be long until they are quicker than their V8 predecessors at the current rate of development.
@FerrariFan: The rumblings in the paddock are that Renault are once again searching for power, yes. I don't know where Horner is quoted as saying that but, if it's true, it's another huge mountain for Red Bull to climb.
@JeB: I can categorically tell you that will not be happening. What those reports failed to mention is that Sainz had a seat fitting two weeks earlier. Both men were likely having seats fitted for show runs etc this year.
@drynog: That is true, but in the long run Honda is spending less money and can focus all its resources on one team. No point looking at this with such a short-term outlook - McLaren-Honda formed together to win a championship at some pointsoon, not to be the best team from the first race in 2015.
@FerrariFan: OK, I had not seen it. In that case it's a pretty big deficit!
@JeB: He's one of the most interesting stories going into the new year. He seems completely unfaed by the pressure so far but it's too early to predict how he will do until we know how competitive Toro Rosso is. The team is aiming for a best-ever finish of fifth in the constructors.
@FerrariFan: They aren't "sandbagging". There's no point doing that at this stage because testing is where the teams work out where the limits are in both its aero package and engine. Ferrari is probably happy because its running through its programme without many reliability gremlins so far.
Anyone who follows this chat will know how irked I get by the term sandbagging. Especially in testing. One slowish lap and immediately everything is "sandbagging". Testing isn't just about headline times - nor is Free Practice later in the season