This page - updated throughout the day, with newest posts at the top - brings you the key news and information from the first test session of the year at the Circuit de Barcelona-Catalunya...
Day four at a glance
It's Ferrari from Red Bull and Renault as the first pre-season test of 2017 wraps then.
Times weren't quite as fast as day three, when both Ferrari and Mercedes dipped under the 1m 20s mark - but even so Raikkonen's lap is the third quickest of the test, and enough for him to wind up almost a second clear of the field.
The Scuderia's slick day contrasted with Toro Rosso and Williams, who managed one full lap between them.
For a full report on the fourth day, click here...
As the sun sets over Barcelona, as that's left to say is thanks for joining us this week. There's not long to wait for the second test... just a few days in fact, with track action resuming on 7-10 March. See you then.
Ferrari fastest as first test wraps
Ferrari do indeed top their second day of the 2017 pre-season - which means honours are split evenly between the Scuderia and Mercedes after the first four days in Barcelona.
The top seven finish the day covered by just 1.7s, while the 10 teams collectively rack up 687 laps.
Toro Rosso don't contribute much to that tally however - they lost effectively the entire day with technical gremlins, discovered after just one installation lap when the circuit had been soaked to permit wet tyre testing.
Late flyers... but not at Mercedes
Sauber are suddenly in amongst the frontrunners, as Antonio Giovinazzi bolts on the purple-marked supersofts and jumps to fourth. It's a fleeting feeling though - Romain Grosjean goes 0.093s to bump the Italian down one spot. Both men trail Palmer meanwhile - the Briton has got his Renault to within 1s of Raikkonen's benchmark.
The top three have all set their best times on the yellow-marked soft.
As teams up the pace, the Silver Arrows appear to be satisfied with their day. Bottas is out the car and heading to media sessions as we move into the final minutes.
Raikkonen shifts the goalposts
Twenty minutes of testing to go, and Kimi Raikkonen improves to extend his advantage at the head of the field. Times aren't on a par with yesterday, but the Finn's new best of 1m 20.872s puts him almost a second clear of the chasing pack.
Set on the yellow-marked soft tyre, it's the third fastest time we've seen across the four days.
Vandoorne vaults up the order
After a troubled beginning to the week, McLaren look to be ending the first test on a much more positive note. Stoffel Vandoorne has clocked more than 60 laps today and with the ultrasoft tyres bolted onto his MCL32 he's just gone fourth fastest.
Practice makes perfect
It's not just the cars that are put through their paces at testing...
Raikkonen reasserts Ferrari authority
We said Verstappen's marker could take some beating, but as it happens it takes no time for Kimi Raikkonen to put Ferrari back on top of the pile. Will we see further movement at the top of the timesheet before the end of the day?
Follow minute-by-minute timesheet updates by downloading the Official F1® App and going to Results & Standings > TEST. For more information, click here.
A new leader
Mercedes and Ferrari have dominated the top of the timesheets this week, but could this be the day that fellow title favourites Red Bull end up on top? Max Verstappen pounds round in 1m 21.839s on soft tyres to knock Kimi Raikkonen down to P2. It's not the quickest the team have lapped this week, but it's the new benchmark for today and could take some beating.
Also on the move are Force India's Sergio Perez and McLaren's Stoffel Vandoorne, the former up to P3, the latter to P5.
Max Verstappen had a troop of fans from a local school cheering him on this morning, but there's no doubting who the main man is in these parts - even if he's not actually on duty today. Fernando Alonso's most hardcore fans are still out in force in the paddock and the main grandstand, watching on as team mate Stoffel Vandoorne approaches a half-century of laps of Barcelona.
Mercedes vs Red Bull
Suddenly we have just two cars on track, within a few hundred metres of each other, and it's two of the year's most fancied teams: Red Bull and Mercedes.
Verstappen is the man ahead on track, and he's also lapping faster than the Silver Arrows. Soft tyres for the Dutchman, supersofts for Mercedes' Valtteri Bottas, but lap by lap the Red Bull inches away... until Verstappen heads for the pits to bring the faux head-to-head to a close.
It's impossible to read anything into that of course - but you wouldn't put money against the two teams fighting it out for real once the season gets underway.
Toro Rosso still battling reliability
As several teams rack up the miles now the circuit is dry, Toro Rosso's poor final day becomes ever more exaggerated. The team completed just one installation lap this morning, when the track was at its wettest, before having to pit - reportedly for a precautionary engine change.
They're still stuck on that single lap in the overall count. Every other team has managed at least 33 laps - and Haas lead the way with 75. Not exactly the day Daniil Kvyat would have been hoping for...
In the spotlight
The sun is beating down here in Barcelona, meaning we're under almost entirely dry conditions. Certainly the crossover for slicks has comfortably passed, with every car venturing out now using one of Pirelli's dry compounds.
When they're on duty, a driver's day is dominated by specific run plans, feedback and data - but the benefit of testing is that drivers also get time away from the cockpit. Red Bull's Max Verstappen made the most of it by making a surprise - and unannounced - visit to the Turn 10 grandstands earlier in the week...
The drying process
An hour into the afternoon session and the warm heat of the Barcelona sun has already dried the track considerably - so much so that Romain Grosjean had to search for the wet part of the track when he came down the pit straight.
Slip sliding away
The afternoon session gets underway with a fresh sprinkling of water on the track - and that should mean plenty more of this...
Raikkonen puts Ferrari back on top
In a flurry of late activity, Raikkonen sends Ferrari back to the top of the pile, while Romain Grosjean and Stoffel Vandoorne - their cars both fitted with supersofts - jump up to second and third respectively.
Hulkenberg ends the morning with the most laps completed with 51, while at the other end of the scale Daniil Kvyat managed just a single tour, his Toro Rosso reportedly having suffered a technical issue.
The teams will now enjoy a well-earned lunch break while a fleet of water tankers soak the track once more ahead of this afternoon's wet running.
Mercedes' late entrance
They've missed all of the morning's wet running, and Lewis Hamilton has called an early end to his programme, but Mercedes do make it out before the lunchbreak. Electrical fault fixed, Valtteri Bottas heads out on soft tyres.
Perez races to the top of the timesheet
Sergio Perez and Nico Hulkenberg take positions one and two on the timesheet as the lunchbreak approaches, the former team mates having run closely together on track.
First test over for Hamilton
It's all over for Lewis Hamilton who will leave the first test in Barcelona with an excellent 234 laps and 1,089 kilometres under his belt.
The inside line on today's wet test
Want to learn more about the logistics and objectives of today's wet tyre testing? Allow Pirelli's racing manager Mario Isola to explain...
Raikkonen the first onto slicks
With the Barcelona sunshine having all but dried the track, Ferrari bite the bullet and send Kimi Raikkonen out on slicks. Within a handful of laps on softs the Finn slashes his way down to 1m 25.939s.
Force India get their session underway
Verstappen ups the pace
After a brief pause, during which he offers a wave to the bank of enthusiastic school children in the grandstand opposite, Max Verstappen returns to the track on inters and bangs in the first sub-1m 30s lap time of the day.
Verstappen first to sample inters
The circuit has dried at a rapid pace, and Red Bull become the first of several teams to switch to intermediate tyres. Max Verstappen's first lap is almost two seconds faster than his previous best.
Mercedes, meanwhile, have said on Twitter that they are investigating an electrical fault, hence their lack of involvement so far.
A bit of spray to start the day
It's been a good start to the day for McLaren, with Stoffel Vandoorne putting 18 laps on the board. For more spectacular shots of the Belgian (and his fellow drivers), check out our regularly updated gallery.
Mercedes in no rush to sample wet track
They've topped the timesheets for the two of the past three days, but world champions Mercedes clearly aren't too keen to take to the track in these conditions. The only other team yet to do at least one lap (aside from Williams who are not running at all today) are Force India.
True to form, Verstappen is the fastest of the four drivers to have set a lap time so far. Don't forget, you can follow minute-by-minute timesheet updates by downloading the Official F1® App and going to Results & Standings > TEST. For more information, click here.
Verstappen the first to sample the wet track
His prowess in the wet is well known - remember Brazil? - so it was perhaps unsurprising that Max Verstappen was the first driver to try his hand on the freshly soaked track, his Red Bull kicking up an enormous rooster tail of spray in the process.
How the track was watered
F1 racing is the ultimate in high-tech motorsport - but today's method of wetting the circuit was decidedly rudimentary (though highly effective!).
No running for Williams on Day 4
Williams have confirmed they won't be participating in the final day of running at Barcelona following Lance Stroll's crash yesterday afternoon. "Following a thorough inspection overnight some damage to the FW40 chassis was discovered and therefore, on safety grounds, the team will not run the car today, read a statement from the team. "A second chassis will be prepared at track this afternoon, as originally planned, with the team aiming to be back on track for the second test next week starting on Tuesday 7 March."
Catch up on yesterday's action
Rapid laps from Bottas and Vettel and another pair of offs for Williams' Lance Stroll - here's our video recap of all of yesterday's action.
Wet wet wet
After three days of dry running, the teams and drivers face a new challenge today - a wet track. No, it's not actually been raining in Barcelona, instead the track has been artificially soaked by F1's official tyre supplier Pirelli in order to simulate extreme wet-weather conditions. The circuit will then be allowed to dry during the morning, allowing teams to explore the tyre supplier's new wet and intermediate compounds - and the crossover points between them - ahead of the season.
The men at the wheel
Here's the provisional line-up for this week's final day - with plenty of teams splitting driving duties, it's going to be a longer timesheet today. However, it remains to be seen whether Williams will get their FW40 out on track after it was damaged yesterday when Lance Stroll crashed. For more on the situation, click here.
|Mercedes||Lewis Hamilton (am) / Valtteri Bottas (pm)|
|Red Bull||Daniel Ricciardo / Max Verstappen|
|Force India||Sergio Perez / Esteban Ocon|
|Toro Rosso||Daniil Kvyat / Carlos Sainz|
|Renault||Nico Hulkenberg (pm) / Jolyon Palmer (pm)|