Sebastian Vettel admits there was no obvious indication of what caused his high-speed crash during testing in Barcelona on Wednesday.
Nico Hulkenberg believes Renault must start matching the levels of development that would be expected from a manufacturer works team.
Sergey Sirotkin has praised his time with Williams and admits he feels "sorry" about their recent woes.
Lance Stroll and the Racing Point team hailed a day of progress as the second Formula 1 test began in Barcelona.
Carlos Sainz kept McLaren at the top of the timesheets as a nasty crash for Sebastian Vettel disrupted the Day 2 morning session in Barcelona,
Lando Norris expressed frustration as two reliability issues overshadowed him setting the best time on Day 1 of the second Formula 1 test.
Fernando Alonso will drive the 2019 McLaren at "selected tests" during the upcoming year as part of a new ambassadorial role with the team.
Pierre Gasly insists Red Bull aren't getting ahead of themselves despite a notable day of testing in Barcelona on two fronts.
Kevin Magnussen believes Formula 1's aero changes for 2019 have made a "big difference" when following other cars on track.
The response so far has been fairly muted to the impact of the simplified front wings and other changes aimed at reducing the impact of turbulent air, though Daniel Ricciardo was also cautiously positive in his assessment.
Magnussen, however, gave a glittering review of his first experience behind another car during testing on Tuesday.
"I followed a car today and it really, really feels a lot better than last year," said the Haas driver.
"I heard so many people, even guys from here when the car was just in the windtunnel, a lot of people were saying it wouldn't make any difference, but following a car today I felt a big difference.
"I could actually follow. So it will be interesting to see..."
Like Ricciardo, however, the Dane did admit he was helped by having a superior pace advantage.
"I was a lot faster than the guy I was following, the lap that I caught him, I got past him. I must have been around two seconds faster," he explained.
"In which case you also would have passed him last year, but it just felt very, very, different... much better.
"I was behind him for maybe a lap and a half? Something like that. It felt much better than last year."
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The one question that remains, is whether Magnussen will still be as positive when F1 races properly for the first time in Australia next month, on a circuit notoriously difficult to pass on.
"I'm looking forward to seeing if other tracks are the same," he added, "There's always different factors you might have overlooked so you come to another track and it might be different.
"But first signs are good, I would say, in this following aspect."
Lewis Hamilton suggested there was an improvement to his Mercedes after a series of upgrades were introduced to begin the Barcelona test.
