Five key questions going into the new F1 season
How good is Ferrari driver Charles Leclerc?
Formula One pre-season testing often throws up as many questions as answers and this winter has been no exception.
We identify five key unknowns that will be resolved as the season progresses.
1 How much do Mercedes have in reserve?
The champion Mercedes team kept their cards close to their chest for most of testing, waiting until the last moment for Lewis Hamilton to set a headline time virtually identical to the best of pre-season.
The team spoke of handling issues and drivers Hamilton and Valtteri Bottas were unusually effusive in their praise for chief rivals Ferrari.
Was it all bluster or are the pace-setting team of the hybrid era really vulnerable?
2 Can Charles Leclerc become Ferrari's number one driver?
Ferrari splashed out for four-time world champion Sebastian Vettel after Fernando Alonso had failed to deliver a title for the Scuderia, and the German has likewise been unable to claim the title in four years at Maranello.
Exciting sophomore Charles Leclerc is a surefire future champ if he can deliver on the promise of his debut season with Sauber and it seems a matter of when rather than if he will become Ferrari's top dog.
Vettel didn't face much of a challenge from veteran Kimi Raikkonen over the last four seasons, but Leclerc is likely to be snapping at his heels from the start and it will be interesting to see how the established number one copes.
3 Will Red Bull's switch to Honda engines pay off?
F1's change to hybrid engines heralded the end of Red Bull's dominance, and they have largely blamed a lack of power from Renault for that.
Honda made a stumbling return to F1 with McLaren in 2015, but showed signs of progress with Toro Rosso last year and apparent further improvement in testing.
Red Bull won four races last year - their best haul since 2013 - but will they have the power and reliability to build on that?
4 Can Renault break clear of the midfield?
Such have been Renault's struggles to adapt to hybrid power it's easy to forget they were podium and victory challengers immediately before the switch.
But last year was a big step in the right direction and signing star driver Daniel Ricciardo showed they're committed to future success.
Testing suggests the Enstone team should be the best of the rest again, but the bigger question could be how close they can get to the big three of Mercedes, Ferrari and Red Bull.
5 How will McLaren cope without Fernando Alonso?
McLaren scored 62 points last year - more than double their 2017 tally - but 50 of those came from now-departed talisman Fernando Alonso.
Testing suggests this year's car is an improvement, but the team went backwards after a promising start last year. Carlos Sainz's reputation took a bit of a knock at Renault last season and he and rookie driver Lando Norris have plenty to prove.
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