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).