A new Formula 1 season is upon us with Sebastian Vettel and Lewis Hamilton once again favourites for the championship.
The first week of Formula 1 testing is in the books and, as you would expect, there are more questions than answers as to what lies ahead in 2019.
Some teams appear to be off to a strong and competitive start, while others flattered to deceive in Barcelona, so what can we take away from the first four days of action?
Here are some early observations which you may or may not take with a pinch of salt!
1. Ferrari off to a flyer
Perhaps the only conclusion that can be made with a degree of certainty is that Ferrari does appear very well placed heading into the new season.
From Monday morning the SF90 was at the top of the timesheets and while we have seen the Scuderia do this before, you'll be hard-pressed not to find someone who doesn't think their pace wasn't genuine.
Charles Leclerc and Sebastian Vettel both set their best times of the week using the C3 tyre, the middle compound of the five Pirelli has produced.
Yet they only sit seven-tenths off the fastest time of the week, set by Nico Hulkenberg in the Renault on the softest C5 rubber, which the Italian supplier believes should be 1.2 seconds per lap faster.
It's not like the fastest laps both drivers conducted appeared to be glory runs either.
So with an apparent 0.5s advantage over Renault just from the tyre and with plenty more performance to come is an ominous warning, particularly given the French manufacturer is expected to be the fourth best team.
That performance was also matched by seemingly bulletproof reliability as Ferrari completed just 12 laps less than Mercedes, and they were swapping drivers every day too.
A final note must also go to Leclerc who was completely unphased by his task at hand and was more than capable of keeping up with Vettel in every area.
2. Red Bull-Honda will be a force to reckon with
Ever since it was confirmed Red Bull would be changing to Honda engines for 2019, there have been some refusing to consider the idea the partnership might just work.
However, after Week 1, those doubters should already be pinching themselves after four days of undramatic running which had to be seen to be believed.
It's more than likely that the engine was in a very conservative mode and we don't know if the same unit did all four days, but compared to their expected rivals, Red Bull certainly don't appear to have any major deficits.
The team never reveals their hand in the first week, so to end the test only 0.7s off a Ferrari receiving many plaudits on the same tyre is a very good base from which to start.
Of course, Red Bull has talked up their expectations at every opportunity, but even they will concede most of their ambitions are targeted for the second half of the season.
But, based on the first impression, there's no reason at all why they won't be regular race winners in 2019, particularly with Max Verstappen appearing more focused and more hungry than ever before.
3. Mercedes DO have work to do
Mercedes did Mercedes to an absolute tee in the first test, focusing predominantly on long runs with a car that ran like clockwork.
However, unlike previous years this wasn't a German manufacturer that you knew was simply keeping it all under wraps because something did seem off.
Maybe, it was because Ferrari was doing what the same while also looking fast but even when Lewis Hamilton and Valtteri Bottas did pick it up on Thursday they hardly left anyone in awe.
Are they slow? Of course not. We all know come Australia the fuel will come out, they'll find the magic power buttons and suddenly be competitive.
But they were struggling with the tyres in cold conditions, as highlighted by their inability to find much lap time with the C4 and C5 compounds, and there was just no reason to think somehow they have pace that Ferrari and Red Bull can't match.
4. The midfield is closing the gap
It does appear likely that the top three teams will remain in their private battle at the front, but the midfield may well be in 'F1.25' compared to 'F1.5' to use the analogy suggested last year.
Renault was able to keep in touch with what the top teams were doing but there's no indication yet they will make it a 'big four'.
Hulkenberg's best time on the final day was solid enough but the car failure soon after highlighted why reliability remains an issue and it won't go down well to see the Honda engine complete more laps over the first test.
With strong pace and reliability, Alfa Romeo and Toro Rosso do look capable of keeping up with the French manufacturer, as will Haas when they overcome the reliability niggles and start using the softer tyre compounds next week.
5. The curious cases of McLaren and Racing Point
McLaren promised they had worked on reliability for testing and that was the case as they managed 445 laps, much higher than the figures of recent years.
However, performance does seem lacking with their best time of 1m18.4s on the C4 tyre, 1.1 seconds slower than Hulkenberg's benchmark on C5.
So while it would appear they have made some progress, it will be interesting to see where that puts them in the eventual competitive order.
As for Racing Point, they disappointed with lap times well off the pace set by their expected midfield rivals and a lack of running with just 248 laps to their name.
2019 is thought to be a building year for the team in their new guise and financial position, but even so, a greater impact was still expected.
6. Williams at rock bottom
Where to start with Williams... It was thought last year's disaster couldn't get worse yet, three weeks before the start of the new season, it seems that might be the case.
Having missed the first two-and-a-half days, the new car finally got on track meaning, hopefully, they can now focus on catching up but it really doesn't bode well for their competitiveness.
The question I have is how could Williams have gotten it so wrong? Given their struggles last year, they could have switched focus to 2019 far earlier than most and put themselves in a good position to make progress.
Instead, we have deputy boss Claire Williams suggesting they have only now learnt their car build plan isn't "fit for purpose".
The only feasible reasons for the delays are either financial, or the team hasn't learnt the lessons of last year which would be even worse.
They can put a brave face on publicly, but behind the scenes, Robert Kubica and George Russell must be wondering what they've let themselves in for.
Having laid the groundwork last week, Formula 1 teams are back in Barcelona for the final four days of testing before the season opener in Australia.
Twelve weeks after the chequered flag fell in Abu Dhabi, Formula 1 returns to the track ahead of a new season for testing in Barcelona.
Teams are gathering at the Circuit de Barcelona-Catalunya for four days of action that will offer the first insights into what 2019 might just have in store.
In a year of change for F1, it's about building that relationship with a new team or partner and weighing yourself up against likely rivals for the months ahead.
As is the case every year, however, testing will likely create more questions than offer answers, so here's what you should look out for in Spain.
Mercedes racking up the miles
Traditionally, Mercedes doesn't always set the fastest lap times during pre-season but they do top the most important chart, distance covered.
With the team facing threats from Ferrari and Red Bull, don't expect this year to be any different with Valtteri Bottas and Lewis Hamilton smashing the 100-lap barrier consistently every day.
Also, Mercedes normally focus their plan on using the harder compound tyres and this year, with Pirelli taking a more conservative approach, that may bring even more benefits than usual.
Will Red Bull & Honda make a fast start?
Perhaps the most important question this week isn't if Red Bull-Honda is on the pace of Mercedes and Ferrari, but how close they can be on the distance chart.
The days of a Honda-powered car struggling to make it out of the garage should be long gone and, in fact, last year Toro Rosso was one of the surprise performers in testing.
But with Red Bull likely to push the limits of cooling further and test more rigorously the Japanese power unit, if they make it through the week largely trouble-free, that would be a very positive sign for what's to come.
The devil in the details
A takeaway from this week's car launches was how relatively simple most looked with several teams simply opting to mix last year's chassis with this year's wings.
During a shakedown at Fiorano, however, Alfa Romeo offered a first look at how designers may have interpreted the new aero rules with a unique front wing concept.
Therefore, it will be interesting to see if other teams have followed the same path and what other innovations designers have come up with that were not included at the launches.
Are McLaren and Williams back in the game?
Having struggled so badly last season, it wouldn't be too surprising to see McLaren and Williams push a little harder than the rest to evaluate their progress.
For Williams, the problems have already begun after revealing they won't be ready to run on Monday, and at McLaren, there are the recent problems with unreliability in pre-season to overcome.
As a prediction, McLaren certainly appears in a better position to move forward compared to 2018 and one of the tricks to gain an indication of that will be to track their long-run pace.
Can Robert Kubica last the distance?
Staying at Williams, and plenty of attention will be on Robert Kubica making his much-anticipated comeback to Formula 1 after eight years.
While there has been assurances and reassurances that the Pole is more than ready to return, it will be interesting to see if Kubica can match the distance covered by teammate George Russell and do so while remaining competitive.
It is also notable that Williams is the only team to have split their days across two drivers, though there's nothing to read into that at this stage.
Will Renault show any of their significant gains?
Renault has also been the talk of many ahead of the 2019 season, as F1 waits to see if Daniel Ricciardo's decision to join from Red Bull was the right one.
The French manufacturer has also been boosting expectations by touting progress both in the engine and chassis department as they look to close the gap to the top three teams.
So will they offer any signals to back up their talk in testing? In single lap performance likely not but distance covered and long run pace will likely be the areas to follow.
Watch for midday flyers
After cold temperatures and even snow hampered testing last year, the forecast is set fair this week with sunshine and the thermometer reaching the mid-teens.
While still not fully representative of the conditions at most races, it will mean the hour before lunch will be reserved for lower fuel single lap efforts on softer compounds.
How helpful will these times be in making conclusions between the different teams? Not very. But it may offer a chance to see if the 2019 cars will match the speed of their predecessors or whether F1 has taken a step back this season.
At InsideRacing we'll be providing reports all four days and observing the action as it happens via Twitter (@InsideRacingcom).
