Fastest lap: 1:19.333, Lewis Hamilton, Day Four, Mediums
Mercedes continue to set the standards when it comes to F1 Testing and, while Barcelona's unhelpful weather meant there were fewer relentless 100-plus lap days this time, the W09 was ominously impressive when it was on track.
Topping winter timesheets has not always been the four-time champions' game but Lewis Hamilton's afternoon surge to a 1:19.333 on medium tyres was the lap that everyone was talking about after week one. And that almost certainly includes their would-be title rivals.
Kidology or not, Ferrari's Sebastian Vettel is almost certainly correct when he describes Mercedes as the "favourites" for more glory in 2018 and even Hamilton, careful to put a number of caveats against comparisons to 2017, had to admit the W09 "definitely" felt better than its double title-winning predecessor.
Reliable and already clearly fast, the 2018 Mercedes has put down the winter's first significant marker.
Fastest lap: 1:19.673, Sebastian Vettel, Day Two, Softs
Ferrari may have been edged out by Mercedes on both the pace and mileage charts on Day Four, but there is little evidence to suggest a change in the status quo, nor a diminished Scuderia threat in 2018. Indeed, it was Vettel who set the early running - his Tuesday marker eventually three tenths down on Hamilton's quickest lap.
The SF71-H represents evolution rather than revolution for Ferrari and it was always going to be difficult to make a similar performance jump from 2017 to 2018 as they did in the previous off-season. However, Vettel is already suitably impressed, with the four-time world champion confident of ending both his and Ferrari's lengthy title drought.
It was a solid if not spectacular week for Ferrari - understandable given the conditions - but their new challenger still looks mightily impressive and should be Mercedes' biggest obstacle again. Now roll on to Test Two when the battle should really hot up.
Fastest time: 1:19.854, Stoffel Vandoorne, Day Four, Hypersofts
So far, so good for McLaren as they embark on what they hope is a successful journey with Renault. Plenty of laps (they were the only team to venture out somewhat consistently on Wednesday's snow day), the third fastest time of the week; they surely would have taken that ahead of the start of F1 2018.
The impressive beginning was all the more welcome after the disastrous three pre-season tests they endured with Honda, and the team already insist there is "no debate" over whether the switch to Renault power was the right one.
The most laps completed per team after Day Four
|Team||Number of laps|
The drivers seem happy too. Stoffel Vandoorne set McLaren's fastest lap of the week, while Fernando Alonso insisted the new Renault partnership had "huge potential". It's good to see the Spaniard smiling and optimistic again.
There is still a sense that McLaren might yet be fighting with Renault more than Red Bull, but it looks like the sport's eight-time world champions will at least be competing for podiums again - and there are plenty of upgrades on the horizon too.
Fastest lap: 1:20.179, Daniel Ricciardo, Day One, Mediums
Red Bull started fastest and went longest but ended Test One behind familiar foes Mercedes and Ferrari on the combined timesheet. Cause for early concern?
Well, perhaps not, as while they were putting degrees on it, the team appeared quietly content with the RB14's early running. The team were "reasonably happy" while Max Verstappen said he was "quite happy" despite a tricky final day which sent them tumbling down the mileage charts. While the lack of running in the rain was a tactical move, a small afternoon technical glitch and then a day-ending spin for Verstappen were not.
But sources close to the team have indicated that Red Bull feel they are in decent early shape in attempts to close up on their two greatest rivals. Test Two will tell us rather more.
Fastest lap: 1:20.317, Kevin Magnussen, Day Four, Supersofts
Haas surely started the week hoping to reinforce their place in the midfield rather than falling back. They finish it with the sixth fastest driver and a time that was quickest of all on the supersoft tyre.
Now, Kevin Magnussen's Day Four effort probably was not representative when looking at the whole week - Friday afternoon was described as the only period that was even slightly suitable for the 2018 cars, while Romain Grosjean finished as the grid's second slowest driver - but the US team still have to be reasonably encouraged.
The team ended 2017 development early to focus on the VF-18 and this was a reliable start to the year, even though Magnussen completed more than half of the team's total laps for the week on the final day.
"We're happy with what we're seeing and we have something to work with," Magnussen said.
Fastest lap: 1:20.547, Nico Hulkenberg, Day One, Softs
A solid start to a year in which Renault want to start showing signs they could be capable of pushing F1's big boys again. The yellow RS18 certainly looks the part and the winter focus on engine reliability allowed the team to run without too many interruptions as they finished in the middle of the week's lap chart. On that side, team chief Cyril Abiteboul described it as "the best start we've had since the introduction of the V6 in 2014".
How to follow Test Two on Sky F1
|Tuesday March 6||Sky F1 digital live blog, SSN updates||9pm: Paddock Uncut||9:15pm: Ted's Notebook|
|Wednesday March 7||Sky F1 digital live blog, SSN updates||9pm: Paddock Uncut||9:15pm: Ted's Notebook|
|Thursday March 8||Sky F1 digital live blog, SSN updates||9pm: Paddock Uncut||9:15pm: Ted's Notebook|
|Friday March 9||Sky F1 digital live blog, SSN updates||9pm: Paddock Uncut||9:15pm: Ted's Notebook|
In the team-by-team rundown of fastest laps they were only sixth, but little truly can be drawn from a week in which the poor weather made heavy weather of teams' testing job sheets. Carlos Sainz was chasing a better balance on the car when he drove on the final afternoon and it is that kind of work which will be easier to accomplish in the expected more consistent conditions at Test Two.
Fastest lap: 1:21.142, Lance Stroll, Day Four, Softs
A steady week for Williams, and a week where their drivers naturally attracted most of the attention.
Even though this was only pre-season testing, the pressure was on Sergey Sirotkin as he sought to ease his way into F1, all the while Robert Kubica was lurking on his return to the paddock. The two drivers actually set their fastest times on the same day and on the same tyre, with reserve driver Kubica more than three tenths of a second faster than the rookie. But other than that, it was difficult to read into Williams' test - they should have enough to hold off teams such as Toro Rosso and Haas come the start of the season but may still be adrift of Renault, McLaren and Force India.
Still, Paddy Lowe seemed content with the work, declaring: "We've recorded huge amounts of data and we've achieved a lot of very reliable running without any failure."
Fastest lap: 1:21.318, Pierre Gasly, Day Two, Softs
While Toro Rosso talked a confident game as they prepared to start life alongside Honda in Barcelona, even they must have been pleasantly surprised by their new engine suppliers' progress here. A year on from Honda's disastrous first week of testing with McLaren, Toro Rosso have racked up more laps than any other team so far and finish Test One with quicker times than Force India and Williams. Is the Japanese firm's potential finally going to be unlocked, and might McLaren even rue switching to Renault power?
"The good thing about what we saw from Honda last year is despite all the difficulties they had over the first half of the season they still had the capacity to develop the power unit," Toro Rosso's technical chief James Key told Sky Sports. "As long as that trend continues, there's no reason why they can't genuinely be challenging Renault by mid-season or the end of season."
Key also added that Toro Rosso were happy to give their new partners "freedom" - something Honda certainly struggled with during the plagued three-year spell with McLaren - and though questions remain over the team's outright pace, this was a positive start.
Fastest lap: 1:21.841, Esteban Ocon, Day Two, Softs
This first week of testing may not have been too useful in terms of predicting F1's pecking order for the next season, but surely the team expecting the biggest improvement come Test Two and the Australian GP are Force India.
Usually one of the sport's most consistent and relentless outfits, the perennial overachievers uncharacteristically finished Week One with the least amount of laps. Armed with an ever-reliable Mercedes engine, this was not due to a mechanical issue - but because they used three different drivers on the three days of track action, with Nikita Mazepin filling in on the first day.
This meant that the impressive pairing of Esteban Ocon and Sergio Perez could only complete 79 and 65 laps respectively, with most of those runs focusing on getting used to the new car and aero runs. Due to this, they finished some way down the fastest laps chart.
Expect to see much more of the VJM11's potential next week.
Fastest lap: 1:22.721, Charles Leclerc, Day Two, Softs
Sauber may still be the early candidates to be the start-of-season back-runners, but there are early promising signs that the team are putting their new-found Alfa Romeo sponsorship money to good use.
Along with a vastly different new livery, Sauber have brought forward the biggest change to their 2018 challenger - with a higher front suspension making it, in Ted Kravitz's words, a "very adventurous car".
"It's really impressive what they've done," the Sky F1 expert added.
It was also impressive to see highly-rated rookie Charles Leclerc compare so favourably to the seasoned Marcus Ericsson, while Sauber will be happy to have finished closer to their rivals on lap time, and fourth on the total mileage charts at the end of week one. With a new Ferrari engine, expect the Swiss team to at least be a lot closer to the midfield this year.
The fastest laps of winter testing
|Lewis Hamilton||Mercedes||Day Four||Mediums||1:19.333|
|Sebastian Vettel||Ferrari||Day Two||Softs||1:19.673|
|Stoffel Vandoorne||McLaren||Day Four||Hypersofts||1:19.854|
|Valtteri Bottas||Mercedes||Day Two||Mediums||1:19.976|
|Daniel Ricciardo||Red Bull||Day One||Mediums||1:20.179|
|Sebastian Vettel||Ferrari||Day Four||Softs||1:20.241|
|Kevin Magnussen||Haas||Day Four||Supersofts||1:20.317|
|Max Verstappen||Red Bull||Day Two||Mediums||1:20.326|
|Kimi Raikkonen||Ferrari||Day One||Softs||1:20.506|
|Nico Hulkenberg||Renault||Day One||Softs||1:20.547|
The Sky Sports F1 Digital team will be providing live commentary from dawn until dusk for every day of the final test while Sky Sports News will also deliver live updates from trackside.