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As it happened: Test day four
By Jonathan Noble, Edd Straw, Glenn Freeman, Ben Anderson, AUTOSPORT staff and Jamie Klein
The live commentary has ended. No further updates will be posted.
07:58 Good morning and welcome to the final day of AUTOSPORT Live's coverage of the first Formula 1 test of winter 2015 at Jerez.

08:00 We've had a Ferrari-powered clean sweep of fastest times so far this week, with Sebastian Vettel kicking off his new career by topping Sunday and Monday, before customer team Sauber's rookie Felipe Nasr pipped Kimi Raikkonen (with a bit of help from some soft tyres) yesterday.

But Nasr was first to suggest that the Mercedes runners aren't showing their hand yet.

08:01 The green light comes on and the track opens for business.

After yesterday's damp start, it's sunny and relatively clear.

08:01 Raikkonen, Lewis Hamilton, Marcus Ericsson and Max Verstappen are first to get down to business.

08:03 Kvyat and Massa head out as well, so we've seen six of the eight cars here today in the first two minutes.

08:05 Ericsson is the first driver to set a time, for yesterday's pacesetter Sauber. It's a 1m58.596s.

08:06 Here's the full driving line-up for the final day of Jerez testing:
Mercedes - Lewis Hamilton
Red Bull - Daniel Kvyat
Williams - Felipe Massa
Ferrari - Kimi Raikkonen
McLaren - Jenson Button
Toro Rosso - Max Verstappen
Lotus - Romain Grosjean
Sauber - Marcus Ericsson

Jos Verstappen08:06 Due to brief finger trouble, our AUTOSPORT leaderboard almost had Jos Verstappen driving the Toro Rosso today. It's been a long week...

08:07 The track is not quite dry enough for total commitment to slick tyres yet. Max Verstappen has just left the pits on inters

08:09 JONATHAN NOBLE: "Today will hopefully give us some more answers about the progress of McLaren-Honda. There were some encouraging signs in terms of reliability yesterday morning - but we never saw any proof of the speed of the car.

"Hopefully a bit of dry running later on will allow us to see just how quick it is - and whether Honda and McLaren can really deliver on their winter optimism."

08:10 Romain Grosjean makes his first appearance of 2015, taking over the Lotus E23 from team-mate Pastor Maldonado for the first day.

AUTOSPORT asked Maldonado if he had a message for his team-mate overnight based on his experience of the car, but unfortunately all we got in response was: "No message, just work through the programme." Disappointing.

08:12 The McLaren - which was out bang on 9am yesterday - is the only car we haven't seen yet this morning.

08:14 Kvyat heads out for a second lap. He'll be hoping to return with his front wing in tact this time, after he damaged Red Bull's only wing on day two and had to run without one on the RB11 for the rest of the day.

08:17 To no one's surprise, Ericsson's 1m58s benchmark doesn't survive for long at the top. Kvyat's first timed effort is a 1m37.799s.

08:18 We have a Honda engine being warmed up in the McLaren garage. That doesn't cause quite as much excitement in the Jerez media centre as it did on the days when Fernando Alonso was in the car instead of Jenson Button, but we're just as interested regardless.

08:20 Kvyat finds a few more tenths to get down to a 1m37.1s. The Red Bull sparks across the finish line a lap later having slowed to a 1m38.4s.

08:20 Wheel guns are at work in the McLaren garage...

08:22 We have eight cars in the pits at the moment, so we've sent BEN ANDERSON down to peer around the screens at the front of the garages.

08:23 @HondaRacingF1: "It's time. The engineers are finishing up. Now it's down to @JensonButton and the power unit. #McLarenHonda"

08:25 BEN ANDERSON reports that there are thumb-up all round from the McLaren mechanics, so it should be any moment now,

08:26 As the McLaren fires up, Hamilton passes its garage and pulls up to perform a practice start. Button edges out into the pitlane, but the Honda engine is now off and he's being wheeled back into the garage.

08:28 Hamilton does a pass-through the pits and performs another practice start. We've got Ericsson, Massa and Grosjean out on track too.

08:28 BEN ANDERSON reckons Button simply stalled the McLaren as he was pulling out of the garage. Perhaps Hamilton's arrival was a distraction.

08:31 Ericsson cruises past the pits, posting a 1m48.586s in the process. In what appears to be a 'slow-off', Massa crosses the line at a lower speed, but posts a slightly faster 1m46.701s. Now Grosjean is in on the act - coasting by to post a 1m58.257s.

08:32 Button succeeds in getting the McLaren out on track at the second attempt.

08:33 BEN ANDERSON says that when the Honda engine cut out earlier, the mechanics tried to get it to re-fire out in the pitlane, but they had no luck. There was no panic from the mechanics, and sure enough just a few minutes later everything is back up and running.

08:34 BEN ANDERSON: "McLaren is known for its fastidious cleanliness. Mechanics spray clean the tyre marks left by Button's winter hard-compound Pirellis as soon as the car has left the garage."

08:35 Button returns, and the McLaren is backed into its garage having completed its first installation lap of the day.

08:36 Ericsson is still circulating, and getting closer to Kvyat's benchmark. The Swede is down to a 1m38.739s now, with eight laps on the board already.

08:37 Is this the start of a race simulation for Hamilton? He's performed a few practice starts, and before his latest one he appeared to even be including the long wait at the front of the grid as part of the procedure.

08:41 Button has climbed out of the McLaren. BEN ANDERSON says there is a lot of attention at the rear of the car from the mechanics.

08:42 Scratch our race sim suggestion for Hamilton. He's back in the pits. Practice start work only for now then.

08:43 The bodywork has been taken off of the MP4-30 as McLaren and Honda people start to have a proper look around.

08:44 We have our first red flag of the day.

08:45 Kvyat, Ericsson and Verstappen are out on track at the moment. EDD STRAW has spotted the Sauber still on the move.

08:45 Verstappen returns to the pits, so it's the Red Bull of Kvyat that has stopped. He's in the middle sector.

08:47 The flatbed truck is deployed to recover the Red Bull, and not for the first time its driver decides to head the wrong way around the circuit.

08:48 The recovery truck has pulled up at the entry to the chicane, on the left-hand side of the circuit.

08:48 Red Bull mechanics have been deployed from the pits, complete with rubber gloves and a car cover.

08:49 The truck has carried on around the track, minus a Red Bull, so we're stumped as to why it stopped near the chicane.

08:50 @McLarenF1: "Jenson's completed his installation. Now waiting for the track to dry a little..."

Daniil Kvyat08:52 The Red Bull is stopped at Turn 9 - the first of the double-right before the chicane.

08:53 We had an incident at Turn 9 causing a red flag yesterday morning as well, when eventual pacesetter Felipe Nasr spun the Sauber into the gravel while the track was wet.

08:54 Kvyat has returned to the pits before his car. BEN ANDERSON reports that he's making some strange hand gestures - "looks like he's squeezing an orange" - apparently.

08:56 We have a flatbed in the pits. The Red Bull has been recovered, so we should be good to go shortly.

08:57 The track is open. Not much of a rush to get out.

08:59 BEN ANDERSON is doing his best to assess (some might say guess) the state of the Red Bull under its cover. He can't see any obvious signs of damage, so it must be something to do with the oranges Kvyat was gesturing about earlier.

09:01 Ah ha - our detective spots "tell-tale stones" on the back of the recovery truck, suggesting the Red Bull might have repeated Nasr's trick from yesterday and been through the gravel. Alternatively, the truck's operators couldn't be bothered to clean it from yesterday.

09:01 Verstappen heads out for another Toro Rosso practice start. The Italian-based team has certainly given its clutches a work out this week as it tries to acclimatise an all-rookie line-up to the basics of Formula 1.

09:03 Verstappen sets the new fastest time of the day - a 1m37.710s.

09:07 BEN ANDERSON has noticed a difference in how the teams go about covering their cars during a recovery process. While Sauber had a basic cover that just went over the top of the C34, Red Bull has a more complex two-piece set-up that also covers the bottom of the car for when it is lifted up off the truck.

09:08 That's reminded us of a Barcelona test a few years ago, where as Red Bull was packing its car away into one of its trucks, photographers were able to stand underneath the tail lift and get all sorts of shots of the underside of Adrian Newey's latest creation. It caused plenty of panic for the crew members who were trying to pack the car away.

09:15 Verstappen continues to plod round. Team-mate Carlos Sainz Jr managed 137 laps yesterday, and we've heard that Toro Rosso is targeting 160 today.

However, Renault's problems at this test, caused by a 'stupid part', have prevented either of its teams from doing particularly long runs. Perhaps Toro Rosso will push the boundaries on that front a bit more today, given the mileage it has racked up.

09:15 More improvements for Verstappen at the top - he's down to a 1m35.962s now.

09:16 Hamilton heads out on a set of intermediates, so there must be some damp patches out there still. We have blue skies at Jerez though, so hopefully the sun can dry the track out pretty quickly.

Max Verstappen09:16 Another few tenths found by Verstappen - he leads the way with a 1m35.551s.

09:18 @Lotus_F1Team: "It's a little moist on track so we're biding our time, and resting our minds, till it's appropriately dry out there. Time for a cuppa"

@SauberF1Team: "The track is still damp in some places therefore hardly any cars out there. #ME9 in the garage."

@MercedesAMGF1: "Quiet start to the day: a tad greasy out there but the sun's out & there's dry lines appearing...#StayTuned"

09:19 Verstappen finds another tenth out front, while Hamilton posts his first lap of the day. He's 3.3s slower than the Toro Rosso with a 1m38.818s.

09:20 Verstappen must be doing a good job of drying the track out for everyone else - he improves again to a 1m35.221s.

09:21 Raikkonen - yet to set a time today - joins Verstappen and Hamilton on track.

09:24 Here's a lap count, we're sorry we can't include this in our times box - we know there have been plenty of requests for that:

Verstappen - 18
Ericsson - 17
Hamilton - 11
Kvyat - 8
Grosjean - 5
Massa - 4
Raikkonen - 3
Button - 1

09:24 Raikkonen's first flying lap of the day is a 1m33.022s, comfortably fastest.

09:25 Hamilton improves to a 1m37.382s.

09:27 Everyone is still on intermediates at the moment. Ferrari appear to be ready to receive Raikkonen back in the pits soon - mechanics and screens are ready.

09:28 Hamilton improves again to a 1m36.286s, and BEN ANDERSON says helmeted mechanics are waiting around a pit box marked out with cones for what looks like some pitstop practice.

09:28 BEN ANDERSON: "Lots of work still going on at McLaren. Bodywork is still off the car so it's not coming out any time soon, it seems."

09:29 No sign of Hamilton coming in for that dummy pitstop yet - he improves to a 1m35.757s, and follows up with a 1m35.511s.

09:32 Mercedes have a set of mediums ready for Hamilton, so he's ditching the inters.

09:33 Remarkably, we have three cars on track and they're running nose-to-tail. Raikkonen leads Hamilton, with Verstappen at the rear.

09:34 Hamilton passes Raikkonen at the final corner, while Verstappen heads down the pitlane for another practice start.

09:34 Ericsson joins Hamilton in taking to the track on slicks, as the world champion is about to set the fastest time of the day.

09:35 Hamilton's first flying lap on slicks is a 1m28.977s.

09:36 BEN ANDERSON reports that there's not much activity at Lotus, with the car up on its stands and the garage door only slightly open. Perhaps if Hamilton's run convinces the team that the track is dry, then we'll see Grosjean out soon.

09:37 Hamilton improves again - this time it's a 1m27.943s.

09:38 BEN ANDERSON: "Kimi is in and the screens surround the car immediately. I've noticed there is a specific engine rev procedure for the SF15-T before it is switched off: two bursts, a pause and then a longer burst, then off."

09:40 It's been chilly all week here at Jerez - current air temp is 8.9C, track temp is 11.7C.

09:40 Another improvement for Hamilton: he finds another three tenths to set a 1m27.6s.

09:42 BEN ANDERSON has spotted Marcus Ericsson out of the car at the moment. Plenty of work going on at Sauber so it doesn't look like a run is imminent.

09:44 Our man corrects himself - declaring that the Sauber's yellow sidepods are being bolted on and Ericsson is getting ready. Does that count as reading too much into testing, or can we only say that about the laptimes?

09:44 Hamilton goes faster - 1m27.360s.

09:46 SAUBER FACT: Heinz-Harald Frentzen was the first driver to finish on the podium for Sauber thanks to his third place in the 1995 Italian GP.

09:46 Williams only has four laps to its name today, and BEN ANDERSON tells us that it's all quiet in the team's garage. The car is up on stands, tyres are in their blankets, and Massa's helmet is on a shelf by the car. A pitwall spotter has just been called back into the garage.

09:46 We have noise from the McLaren garage again. The engine is going through a lengthy and varied warm-up.

09:47 On track, Hamilton dips under the 1m27s bracket with a 1m26.998s.

09:47 Raikkonen finds nearly six seconds with his first proper run in the dry. He slots in just under 0.4s slower than Hamilton.

Jacques Villeneuve09:48 SAUBER FACT: Three drivers have started their 150th world championship grands prix while driving for Sauber: Jean Alesi, Heinz-Harald Frentzen and Jacques Villeneuve. AUTOSPORT'S GLENN FREEMAN will enjoy that fact.

09:48 BEN ANDERSON tells us that there's a lot of work going on in the Red Bull garage.

09:49 Hamilton improves to a 1m26.701s, but seconds later he is deposed from the top by Raikkonen's 1m26.307s.

09:51 Kimi Raikkonen goes to the top of the times - 1m25.208s.

09:52 Verstappen improves to 1m27.423s.

09:54 Alarming late pit entry for Verstappen - he cuts across into the pit entry as he exits the final corner. The car has come to a stop.

09:54 For those not familiar with Jerez, the pit entry is BEFORE the final corner, so Verstappen clearly made a last-minute call as he felt something was up with the Toro Rosso, which is now being pushed down the pitlane.

09:55 @redbullracing: "8 early laps for Dany on Day 4 in Jerez before the car stopped on track. The Team are investigating as we speak... "

09:57 Improvements for Raikkonen and Hamilton. The Ferrari leads the way with 1m25.011s.

09:59 Grosjean is back on track in the Lotus, which is yet to set a representative time today and currently sits 20 seconds off the pace.

10:00 Guesses from the AUTOSPORT team of a 1m27s or a 1m31s for Grosjean. He plonks himself in the middle with a 1m29.526s.

10:02 We've just passed 11am on the final day of testing. Here's a lap count update:

Hamilton - 36
Verstappen - 28
Ericsson - 21
Raikkonen - 21
Grosjean - 8
Kvyat - 8
Massa - 4
Button - 1

10:02 Grosjean delivers a 1m27s at the second attempt, leaving him 2.5s off the pace set by Raikkonen.

10:02 EDD STRAW: "Apparently there were no problems for the Williams. The team was waiting for the track to dry."

10:03 Grosjean is up to third with a 1m27.255s.

10:04 Sure enough, Williams sends Massa out for an exploratory lap. Let's hope the team decides the track is dry enough for the FW37 to get to work.

10:06 SAUBER FACTS breaking news: we've told EDD STRAW that by the end of today he must have produced at least one random fact about every team that is at Jerez this week. Sorry, Force India fans.

10:06 Two more improvements from Grosjean, he's down to a 1m27.097s.

10:07 Verstappen has headed back out. So the earlier problem wasn't a significant one.

10:07 Hamilton improves to a 1m26.111s. He's still second fastest.

10:07 Grosjean gets into the 1m26s bracket for the first time.

10:08 Ericsson goes fourth fastest on a 1m26.891s.

10:09 All seems fine for Verstappen. He's continuing onto his first flier of the run.

10:10 Ericsson moves Sauber up to P3.

10:10 RED FLAG

10:11 Verstappen returns to the pits, so the Toro Rosso wasn't the problem.

10:11 Hamilton has stopped.

10:12 The Mercedes is at the chicane, and Hamilton is out of the car.

10:13 The flatbed truck and a car-load of Mercedes mechanics make their way to retrieve the car.

10:14 The angle that Hamilton's car is parked at suggests that this was not a simple case of grinding to a halt. Parked at 90 degrees to the track.

10:14 McLaren watch: BEN ANDERSON tells us that the team is hoping to be out in 5-10 minutes. It had to take the floor off of the MP4-30 to check something relating to the Honda engine.

10:15 BEN ANDERSON has overheard a Mercedes mechanic speculating that the car might have "run out of jungle juice".

10:17 A picture Tweeted by our snappers @LATphotographic shows Hamilton stood by his Mercedes, with mud on the left-rear tyre and the car facing the wrong way in the middle of the chicane.

Lewis Hamilton10:17 Hamilton is back in the pits - helmet still on - as the crowd cheers his arrival.

10:22 @MercedesAMGF1: "Bit of an intermission as the car is fetched from an unusual parking spot between T11/12. Just awaiting her return now..."

10:23 The flatbed returns to the pits with a Mercedes F1 W06 on its back.

10:24 The track is green again.

10:25 Verstappen is the first car to return to the track with - you guessed it - another Toro Rosso practice start.

10:28 Verstappen goes fastest with a 1m24.705s.

10:29 Raikkonen trumps Verstappen with a 1m24.104s, while Grosjean and Massa also post new personal bests further down the leaderboard.

10:30 Massa improves again, jumping up to fourth.

10:31 A new best for Raikkonen at the top - 1m24.034s

10:32 Now Raikkonen breaks into the 1m23s - on medium tyres.

10:32 Massa keeps building up in the Williams - a 1m25.508s puts him third.

10:33 Button re-appears in the distinct-sounding McLaren-Honda.

10:34 Tiny improvement for Raikkonen moves him onto a 1m23.8s.

10:35 Button stays out to start a second lap on this run in the McLaren.

10:36 The McLaren's first time of the day is a 1m30.706s - 6.8s adrift of Raikkonen.

10:38 Button returns to the pits with four laps on the board for McLaren-Honda today.

10:39 On the subject of laps completed, here's a lap count update:

Hamilton - 43
Verstappen - 39
Raikkonen - 30
Ericsson - 25
Grosjean - 23
Massa - 10
Kvyat - 8
Button - 4

10:41 And here's the headlines from today's action so far:

* Hamilton brings out red flag with spin at the chicane
* Limited running again for Red Bull as Kvyat stops on track
* Raikkonen fastest for Ferrari on medium tyres
* McLaren-Honda completes only four laps so far

10:42 Grosjean briefly has the track to himself, but Raikkonen is now at the end of the pits preparing for a practice start.

10:46 Big news this morning in the world of Formula 1 surrounding the future of the Marussia team, which has paid its 2015 entry fee:

Marussia closes on surprise return for 2015

10:48 Just Massa and Grosjean - P3 and P4 in today's standings - are circulating at the moment.

10:50 Hamilton is back out in the Mercedes, just 40 minutes after he brought out a red flag when he was facing the wrong way at the chicane.

10:52 All cars have headed back to the pits as we approach midday, so it's all quiet here in Jerez now.

10:54 This pause is a good opportunity for CRAIG SCARBOROUGH to answer another one of your technical questions.

10:55 @Dan1Ra1kkonen asks: Can you tell us something about new hydraulic suspension? It's very important after the FRIC ban.

CRAIG SCARBOROUGH: "To create the springing effect of the suspension you can use metal springs (coil spring or torsion bars) or a hydraulic spring.

"Both can be tailored to create the ideal spring effect. Metal springs are simpler, less ‘tunable’, but reliable, whereas hydraulic springs can be packaged elsewhere on the car and can be tuned in situ, but risk unreliability.

"I doubt either is a huge performance differentiator."

10:56 Habitual practice starter Max Verstappen breaks the silence and heads back out in the Toro Rosso.

11:00 Verstappen sets his best laptime of the day so far on that first flier on this fresh set of medium Pirelli tyres. He's closed to within half a second of Raikkonen's benchmark.

11:01 Verstappen is slightly slower next time around. Faster in the first and third sectors but loses time in the middle part of the lap. A 1m24.5s lap is the result.

11:03 After a lengthy delay with an unspecified engine problem, Button has finally returned to the track in the troublesome McLaren-Honda.

11:04 Raikkonen is back out too, so we have three cars circulating now.

11:06 Grosjean lights up the Lotus' rear wheels on his way out of the pits, while Button manages a personal best final sector as he gets back up to speed in the McLaren.

11:08 Raikkonen sets the fastest lap of the day so far, having improved in the final two sectors of the lap. He found half a second in the Ferrari.

11:09 The 2007 world champion goes faster in the first sector, but loses a tenth and a half compared to his previous best overall on the next lap.

11:09 Grosjean's gone faster in the Lotus, though. He's still fourth fastest, but now only just over a tenth slower than the Williams.

11:10 Another improvement for Raikkonen, who shaves another tenth of the best time of the day so far.

11:11 The McLaren is back in after a short run for Button. Raikkonen is currently setting the pace on the hard Pirelli tyre.

11:11 Grosjean moves up to third in the Lotus E23 with another improvement.

11:15 As if roused into life by Grosjean's lappery, Massa heads out in the Williams and responds with an improvement. Only two tenths between the two Merc-powered cars now.

11:16 An update on the problem keeping fruit-squeezer Daniil Kvyat in the garage:

@redbullracing: "It looks like an ERS problem... The Team are on the case and looking to get Dany back on track soon. #F1"

Massa 11:16 Massa improves again to leapfrog back ahead of Grosjean's Lotus.

11:19 Perhaps Red Bull is again suffering from the weakness of that 'stupid part' in the Renault power unit?

11:22 Ericsson sets two consecutive quicker laps in the Sauber to launch himself up to third overall on the timesheet.

11:25 Hamilton heads back out in the Mercedes, after yet another practice start at the end of the pitlane.

11:27 Hamilton is up to second with a 1m24.177s on hards, but he is knocked down to third by medium-shod Verstappen with a 1m24.155s.

11:28 Hamilton takes second back from Verstappen with a 1m23.633s.

11:29 Button takes the McLaren back out for lap eight of the day.

11:30 Lap eight might not be happening for the Button just yet. Is that a McLaren we see rolling back towards the pit entry?

11:31 Yes, it is. Mechanics head over to retrieve the MP4-30, which didn't get very far before stopping.

11:35 Hamilton's pace has backed off slightly. The reigning world champion is circulating in the low 1m24s. Raikkonen's Ferrari is out on hard tyres and has just broken into the 1m22s for the first time today.

11:37 Raikkonen is fractionally slower next time around, but still faster than anyone else has managed today. Another 1m22s lap for the 2007 world champion.

Raikkonen11:38 He's backed off a bit now. The next lap is a 1m23 as Hamilton pits and leaves the Ferrari with the track to itself.

11:42 As Raikkonen continues to pound around (joined by Grosjean's Lotus), here's a lap count for you:

Hamilton - 52
Verstappen - 52
Raikkonen - 49
Grosjean - 42
Ericsson - 33
Massa - 27
Kvyat - 8
Button - 7

11:43 Grosjean makes an improvement on his 43rd lap of the day. He's back up to third in the times having broken into the 1m23s. Button has also headed back out in the McLaren-Honda. Let's see if he can make it further than the pit exit this time...

11:44 Button completes his out lap. So far so good for McLaren-Honda on this latest run.

11:47 The McLaren-Honda goes faster than its managed so far this week on that lap. A 1m28.550s for Button.

11:47 The 2009 world champion is slower next time around though - back into the 1m30s.

11:49 Verstappen makes a slight improvement, but remains fourth fastest in the Toro Rosso.

11:50 Another 1m28s lap for Button (and a personal best in the final sector), but fractionally slower than his best effort so far.

11:52 Button finds time in the first and third sectors on his next lap and makes another improvement overall in the McLaren-Honda. Now within less than six seconds of the pace.

11:54 Button returns to the pits after McLaren-Honda's fastest run of the test so far. Ericsson and Grosjean are still circulating as we approach 1pm local time in Jerez.

11:59 Ericsson is now solo on track, lapping in the 1m27s in the Sauber.

12:00 EDD STRAW is trackside for us at the moment. He reports that Grosjean's Lotus suffered a "huge lock-up" at the final corner during its last run. Says it looks "uncertain" when turning in.

12:01 Ericsson dives for the pits, so the track is silent again.

12:03 With no cars out at the moment, now's an ideal time to take stock of another eventful morning at Jerez as Kimi Raikkonen takes Ferrari back to the top of the timesheets. Here's GLENN FREEMAN's report:

Raikkonen puts Ferrari back on top

12:04 The pause in action is also a perfect opportunity for CRAIG SCARBOROUGH to answer another of your technical questions.

Stefan Smit asks: "What are 'unmarked Perelli-tyres'? Are they experimenting compounds, or just want to keep a secret?

CRAIG SCARBOROUGH: "They are research tyres of slightly different compound/construction to the usual race tyres."

12:05 Max Verstappen breaks the silence by heading back out in the Toro Rosso.

Ericsson12:06 A few more observations from the founder of SAUBER FACTS, EDD STRAW. Unsurprisingly they are about the C34:

"Looks positive on turn-in but less under control in terms of the rear later in the corners."

12:08 Verstappen is back up to second fastest in the Toro Rosso, after breaking into the 1m22s.

12:11 EDD STRAW will be pleased. Ericsson has just headed back out in the Sauber. Meanwhile Verstappen is still circulating, but has dropped his pace back inton the 1m24s.

12:14 Ericsson locks up at the chicane, but gets away with it. He then posts his fastest time of the day so far in the Sauber. Meanwhile, Jenson Button has ventured back out in the McLaren-Honda.

12:16 The Red Bull is back in action finally, after spending most of the morning stuck in the garage with an ERS problem. Kvyat ventures out of the pits in the RB11.

12:17 Button is straight into the 1m29s on his first flying lap of this run. Pitboard says three more laps for McLaren before Button will pit.

12:18 Button finds a couple of tenths on his next lap. The McLaren has almost cracked into the 1m27s now.

12:19 Kvyat's first flier jumps him ahead of the McLaren. The track is much drier and grippier than the Russian left it earlier.

12:21 Another improvement for the Red Bull, which EDD STRAW reckons looks committed, but with power delivery that is not the most "user friendly".

12:22 Felipe Massa breaks into the 1m24s for the first time today, but remains sixth overall.

12:23 Both Massa and Kvyat are making regular improvements, while Button has just broken into the 1m27s in the McLaren-Honda.

12:24 Button heads back to the pits having set McLaren's fastest laptime of the Jerez test so far.

12:25 Massa's and Kvyat's pace has slowed now. EDD STRAW reckons the Williams was taking too much kerb at the chicane and hammering the floor.

12:29 Kvyat kicks up some spray as he catches the kerb coming out of the final corner. The Red Bull is alone on track right now and lapping in the 1m25s.

12:31 Kvyat makes gains in the first and second sectors of his next lap, but falls just under a tenth shy of an improvement overall in the RB11.

At least he's getting some mileage now - 18 laps completed after ruining his first day in the car with that off and suffering an ERS problems this morning.

12:34 Kvyat pits having completed 12 more laps than he managed this morning. Silence descends on Jerez once more.

12:36 While there's a break in the track action, let's have another technical question for CRAIG SCARBOROUGH.

Button12:38 @midnightotaku asks: What the heck am I hearing from the McLaren as it downshifts?

CRAIG SCARBOROUGH: "When off the throttle there’s a lot of engine management going on to minimise turbo lag and thus make power delivery smoother when the driver picks up the throttle again.

"This sounds like the odd mappings used when team’s blew the diffuser with exhaust gases.

"Ironically, what was good for exhaust-blown diffusers was largely based on anti-lag technology."

12:46 Nose designs on Formula 1 cars have been a huge talking point over the past 12 months with different solutions to tighter regulations up and down the pitlane.

The Toro Rosso STR9 was heavily lampooned for its proboscis nose design in 2014, but has a more elegant solution on the new STR10.

Technical chief James Key says we can expect this to change again before the first race in Melbourne.

"You could race this [nose] tomorrow, but we want to start off with a car that runs because we didn’t get any mileage last year and we want to maximise it so this is a launch-spec car.

"We will have a race-spec car in test three that will look very different to this. Stuff at the front of the car will change. We are still in the windtunnel for Melbourne now so we are pushing the limits."

12:47 The silence is finally broken as Button and Hamilton both head back out for more laps.

12:48 Kvyat and Verstappen have joined in the fun too, so it looks as though the teams have finished their impromptu lunch breaks.

12:50 Button is immediately faster on his first flying lap in the McLaren-Honda. It's only a few hundredths of a second, but every little counts...

12:51 EDD STRAW reports that Hamilton had a big moment at the chicane and may be struggling to warm up his hard Pirelli slicks in the cool conditions.

12:51 No such worries for Verstappen, who falls just short of toppling Raikkonen's Ferrari from the top of the leaderboard.

12:52 The Dutch rookie is on soft tyres though, which would explain his extra speed.

12:53 Button manages to go faster in the first sector, but his overall laptime is a tenth slower than his best. Meanwhile Kvyat breaks into the 1m24s in the RB11.

Hamilton12:55 EDD STRAW is still trackside for us. He's been impressed by what he's seen from Hamilton's Mercedes:

"The Merc looks really strong. Hamilton is committed into the chicane and able to get back on the throttle positively."

12:56 Another slight improvement for the McLaren, which is now into the mid-1m27s.

12:56 Massa has also gone faster in the Williams, breaking into the 1m23s for the first time today.

12:58 Massa goes faster still on his next lap on hard Pirelli tyres, while Raikkonen becomes the first driver to break into the 1m21s today in his medium-shod Ferrari.

13:01 Button makes a quick visit to the pits. EDD STRAW says the closing speed between Hamilton's Mercedes and the McLaren-Honda approaching the chicane is "enormous".

13:04 Button, Massa and Raikkonen have both pitted, so we have Ericsson, Hamilton and Kvyat circulating now.

13:04 EDD STRAW says the Ferrari looked really good turning into the chicane, so perhaps Raikkonen finally has the front-end feeling to the car that he craves.

13:07 A raft of pit visits have left Kvyat the only man circulating now, as the first pre-season test of 2015 enters its final three hours.

13:10 Kvyat tags out and hands the track over to Hamilton, who performs another of his laboured practice starts in the Mercedes. Proper preparation for Melbourne continues for the reigning world champion.

13:13 Raikkonen heads back out to exploit some more of the Ferrari's positive turn-in. Meanwhile, Hamilton's first flier of this run puts him straight into the 1m24s.

13:16 Hamilton makes a slight improvement to his fastest time on the next lap. Raikkonen improves in the first sector but falls a tenth and a half shy of improving the benchmark time.

13:22 JONATHAN NOBLE has just returned from speaking to McLaren engineering director Matt Morris. He's revealed that Button's programme was interrupted earlier due to an "operational issue relating to the oil level" - we'll leave you to crack that not-so-subtle code.

Morris added that McLaren is doing aero work this afternoon.

13:27 Just Hamilton pounding round at the moment in the Mercedes, lapping in the 1m24s as the sun beats down on Jerez to a scorching 11C.

13:30 Kvyat and Ericsson head out to join Hamilton on track.

13:31 We're due another lap count update, aren't we? Here goes:

Hamilton - 78
Verstappen - 72
Raikkonen - 61
Ericsson - 53
Grosjean - 53
Massa - 41
Kvyat - 35
Button - 31

13:32 Kvyat improves in the Red Bull, but his 1m24.300s still leaves him seventh.

Raikkonen13:35 For those of you following on our mobile site, apologies that we can't give you the live running order table. So here's how things stack up at the moment:

1 Raikkonen 1m21.516s
2 Verstappen +1.0s
3 Ericsson +2.0s
4 Hamilton +2.0s
5 Massa +2.1s
6 Grosjean +2.2s
7 Kvyat +2.7s
8 Button +6.1s

13:48 BEN ANDERSON boldly declared last night that he was going to follow-up EDD STRAW's top 5 Sauber drivers (Robert Kubica won, for those who missed it) with a list of Damon Hill's top 5 races. He says he's got 3 nailed-on, but he hasn't come up with the other two yet.

13:49 Three cars on track at the moment: Verstappen, Ericsson, Massa.

13:49 @SauberF1Team: "After finishing some set-up work, #ME9 is now doing aero scans. Good weather conditions!"

13:56 ‏@Sriharsha03 asks: "#askautosport What do you make of McLaren and Ferrari, as they both said about change of design philosophy?"

CRAIG SCARBOROUGH: "Ferrari has turned a corner, it just needs to catch up the last stretch to Mercedes. The car looks a lot more stable, improved engine power and drivability is helping balance in the turns and the aero looks far more sorted than last year.

"An image of the diffuser covered in flow-viz showed really good flow lines, compared to the disturbed air passing through last year's underbody.

"McLaren is harder to predict as it hasn't run as much. But if its 'size zero' rear end cools as well as it looks aerodynamically, then it could be a similar position to Ferrari after a half a season of on-track development."

13:59 Hamilton, with aero paint on the front-right corner of the Mercedes, goes second fastest with a 1m22.497s on medium-compound tyres. He's just inside one second of Raikkonen's fastest time today.

13:59 Hamilton is four tenths slower that time around, despite setting a new personal best in the first sector of the lap.

14:01 Hello to Karun Chandhok, who has got in touch via Twitter to give BEN ANDERSON some help picking Damon Hill's top 5 F1 races:

@karunchandhok: "@BenAndersonAuto - Damon races : Silverstone 93 & 94, Suzuka 94, Monaco 96, Budapest 97. 2 races here he was leading superbly till DNF"

14:03 Hamilton is hunting down Raikkonen on track at the moment. The Finn proved yesterday with Daniel Ricciardo that he's not particularly interested in getting out of someone's way when they catch him up, but Hamilton has no dramas negotiating his way past the Ferrari.

14:05 Ricciardo's cause yesterday wasn't helped by the fact that he and Red Bull have been nursing troublesome Renault engines all week, as explained in this piece by JONATHAN NOBLE:

The other F1 engine manufacturer in trouble

14:06 Massa finds half a second on a set of mediums, getting him down to a 1m23.116s.

14:09 BEN ANDERSON: "Thanks to Karun Chandhok for his help picking Damon Hill's top 5 F1 races. I've come to my decision now."

14:13 Number 5: 1998 Belgian GP
BEN ANDERSON: "His two-year spell at Jordan was not generally Hill's finest chapter, but scoring Jordan's first win in Formula 1 was a special moment in a race fraught with crashes in atrocious conditions."

14:14 Hamilton takes a different line down the start/finish straight to most - he moves over towards the pitwall on the left hand side much earlier than the majority of drivers we've seen in action this week.

14:15 Number 4: 1996 Monaco GP
BEN ANDERSON: "Monaco was not as kind to Damon as it was to his father Graham. After Michael Schumacher crashed on the opening lap, Hill led superbly in the wet until his engine let go."

14:15 Just Hamilton, Massa and Ericsson circulating at the moment.

14:18 Number 3: 1995 Hungarian GP
BEN ANDERSON: "Hill was generally poor in the FW17 and ended up getting sacked because of it, but Hungary was a rare occasion where he totally delivered: pole, win and fastest lap."

14:18 Hamilton is approaching the 100-lap mark for the day, something he missed out on two days ago due to the Mercedes developing a water leak at the end of one of his runs.

14:19 Number 2: 1994 Japanese GP
BEN ANDERSON: "Hill chose this GP as the 'race of his life' in AUTOSPORT. Beating Michael Schumacher in a straight fight in the wet was an exceptional feat."

14:21 Ericsson returns to the pits, meaning the track has fallen silent as we await BEN ANDERSON's reveal of his favourite Damon Hill grand prix performance.

14:23 Red Bull clearly got impatient waiting to hear the result of our Damon Hill top 5, so it has sent Kvyat out for another run - which kicks off with a stop at the end of the pits and a practice start.

14:28 It's not often we see any kind of improvement in pace from a Red Bull this week, but Kvyat has just set a new personal best through the middle sector on his way to going 0.2s faster than he'd managed so far today.

14:29 We have a new overall best in the first sector from Raikkonen...

14:30 And in sector two...

14:31 It's a 1m20.841s for Raikkonen on the soft-compound Pirellis. That's the fastest time of the week - pipping Vettel's best earlier in the week of 1m20.9s.

14:33 Raikkonen pits after that very short run that included the fastest time of this test.

Damon Hill14:34 Number 1: 1997 Hungarian GP
BEN ANDERSON: "This is the race that made every Damon Hill fan's jaw drop. Qualified third, passed Schumacher's Ferrari to take the lead, and would have won easily but for a late hydraulics problem in the generally rubbish Arrows-Yamaha. The drive of a champion."

14:37 Kvyat crosses the line at 266km/h - familar range for the Renault-powered teams this week. As a comparison, Mercedes-powered Massa is also on track and was clocked at 278km/h at the same spot last time around.

14:39 @McLarenF1: "Fuel pump issue for Jenson - but he's got a decent amount of laps done so far. Fixing it now."

14:42 Hamilton finds three tenths on this medium-shod run, posting a 1m22.172s. He's still 1.3s shy of Raikkonen's best on softs.

14:43 That latest improvement also marked Hamilton's 100th lap of the day.

14:44 And with that, here's a run down of the full lap count:

Hamilton - 101
Verstappen - 88
Raikkonen - 79
Ericsson - 76
Massa - 63
Kvyat - 56
Grosjean - 53
Button - 35

14:50 Raikkonen is back out on softs, and his best lap of this run is a 1m21.1s - 0.3s adrift of his time from earlier.

14:51 Raikkonen backs off to a 1m29s before winding things up again - this time he manages a 1m21.9s.

14:52 SAUBER FACTS creator EDD STRAW is running out of time to give us a fact on each of the other teams in attendance at Jerez. We'll keep pushing him.

14:53 Lotus is done for the day (and therefore the first test):

@Lotus_F1Team: "An early bath for us after 53 laps today. The data suggested something was amiss with the Power Unit. Productive first test nevertheless."

14:54 @RGrosjean: "Really good first feeling behind the wheel of the #E23 ! Looking forward to be in #Barcelona"

14:58 Minor improvement from Ericsson, who sits fifth today.

15:03 We also have McLaren packing up early today:

@McLarenF1: "We're not going to complete that fuel pump change before the chequer, so that's our running over for this test."

15:05 Raikkonen lights up the timing screens through sectors 1 and 2 with new overall bests, but he crosses the line one tenth down on his fastest time. He's once again on the soft-compound tyres.

Boullion15:06 SAUBER FACT: Nine drivers have scored their maiden world championship points while driving for Sauber. They are: Heinz-Harald Frentzen, Jean-Christophe Boullion (pictured), Nick Heidfeld, Kimi Raikkonen, Felipe Massa, Robert Kubica, Sebastian Vettel, Sergio Perez and Esteban Gutierrez.

15:08 Raikkonen cools-off, then goes again and manages a 1m21.6s.

15:09 RED BULL FACT: Red Bull's headquarters on a Milton Keynes industrial estate was once a ball-bearing factory (although Red Bull has since added additional buildings to the complex)

15:09 The Ferrari returns to the pits, comfortably fastest so far today.

15:13 Ericsson improves to go third.

15:15 FERRARI FACT: Scuderia Ferrari started out life pre-war as a team running Alfa Romeo machinery.

15:17 Ericsson was on softs for that lap. Raikkonen is also on softs, kicking off this run with another 1m21.1s.

15:20 Raikkonen brings his latest short run on soft tyres to an end.

15:21 Ericsson is still going on his softs, but he's slowed to lapping in the 1m25s.

15:22 TORO ROSSO FACT: Scuderia Toro Rosso is the only team in the history of world championship grand prix racing to have won a race using a customer Ferrari engine.

15:23 LOTUS FACT: The current Lotus team came into Formula 1 in 1981 as Toleman. That season, a Toleman only qualified for a race twice. Since then, the team has raced as Benetton and Renault before being renamed Lotus.

15:24 After a few laps in the 1m25s on these softs, Ericsson has now fallen into the 1m26s on this run.

15:24 ...and now the 1m27s.

15:25 Verstappen leaves the pits. It wouldn't be the start of a Toro Rosso run at this test without a practice start. Talk about 'rookie orientation', to borrow a phrase from the Indianapolis 500.

15:27 Very wide entry into the final corner from Massa, who has emerged from the pits on a set of mediums. Perhaps he's winding up to bang in a quick time?

15:27 Maybe not. He's 1.1s off of Raikkonen through the short first sector.

15:27 McLAREN FACT: Nobody has started more world championship grands prix for McLaren than David Coulthard. He started 150 from 1996-2004

15:29 A 1m24.8s from Massa confirms that he's nowhere near giving us something to get excited about at testing enters its final 30 minutes.

Brundle15:30 WILLIAMS FACT: Martin Brundle once raced for Williams. Literally, once, as he filled in for the ill Nigel Mansell at Spa in 1988 and finished seventh. He almost returned to the team full-time in 1993 before Damon Hill got the drive.

15:31 Another soft-tyre run for Sauber propels Ericsson above Hamilton with a 1m22.019s. That's 1.1s slower than Raikkonen managed, also on softs.

15:34 MERCEDES FACT: Toto Wolff was a keen amateur racing driver in GT machinery. He was part of the line-up that won the 2006 Dubai 24 Hours alongside ex-F1 racers Hans-Joachim Stuck and Dieter Quester.

15:35 We've got four cars on track right now - Raikkonen, Ericsson, Hamilton, Kvyat.

15:35 Kvyat improves his time to a 1m23.975s.

15:40 Nobody is lapping particularly rapidly at the moment. But Verstappen has just headed out in the Toro Rosso.

15:42 Raikkonen is currently lapping in the 1m24s bracket, Ericsson in the 1m27s.

15:42 As Hamilton returns to the track.

15:44 Looks like something has blown onto the track at the exit of the last corner. Not sure what it is but isn't a car part from what we can see.

15:47 Verstappen and Hamilton return to the pits. The debris has been recovered by a diligent marshal.

15:47 And we're back underway

15:48 Ericsson is the first to return to the track.

15:50 Red flag again

15:51 Looks like it's Ericsson. He's stopped on track between Turns 9 and 10.

15:57 @MercedesAMGF1: "RADIO @LewisHamilton: "Before the flag I just want to say well done guys. Great first week back!"

15:58 A predictable reason behind this end-of-test stoppage:

@SauberF1Team: "#ME9 made a check of the fuel system and ran out of fuel, as a result."

Credit to Sauber for being more honest than some other teams who have performed similar "checks" earlier this week and made a bad job of covering them up!

16:00 The track goes green with 11 seconds left on the clock.

16:00 Hamilton's Mercedes and Kvyat's Red Bull head out.

16:01 No sign of a chequered flag just yet. Perhaps we're getting a short extension to the day's running because of that late red flag.

16:01 Now we get the flag. The test is over.

Raikkonen16:03 Kimi Raikkonen ends the day - and the entire test - on top for Ferrari with a 1m20.841s.

16:12 Ferrari enjoys a 1-2 for the week here, with Sebastian Vettel's fastest lap just a tenth behind Raikkonen.

By contrast, McLaren drivers Jenson Button and Fernando Alonso sit bottom of the pile in terms of laptime and distance completed at this test.

Mercedes can leave here very happy - Nico Rosberg and Lewis Hamilton lead the way in the 'laps completed' column.

16:18 That's it from Jerez this week for AUTOSPORT Live. We hope you've enjoyed our coverage for the last four days, and thanks for following the first test with us.

REPORT: Raikkonen fastest for Ferrari on final day

Starting this evening, we'll have news and analysis of what we've seen this week on, with plenty more to come later in the week including the 10 key things we learned here, plus the thoughts of ex-F1 designer GARY ANDERSON.

We'll be back with live coverage from the next test at Barcelona, which starts on Thursday February 19. See you then!

P Driver Team Time
1  Kimi RaikkonenFerrari 1m20.841s
2  Marcus EricssonSauber 1m22.019s  +1.178
3  Lewis HamiltonMercedes 1m22.172s  +1.331
4  Max VerstappenToro Rosso 1m22.553s  +1.712
5  Felipe MassaWilliams 1m23.116s  +2.275
6  Romain GrosjeanLotus 1m23.802s  +2.961
7  Daniil KvyatRed Bull 1m23.975s  +3.134
8  Jenson ButtonMcLaren 1m27.660s  +6.819
All timing unofficial. Updated: 15:36 GMT
Mainly sunny High Temp: 12°C / 54°F
Track: Dry
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