Sebastian Vettel topped the timesheets on the first day of the second test in Barcelona, but there were significant breakdowns at both McLaren and Red Bull.
While Vettel sat pretty at the top of the pile with a 1.20:396 on medium tyres and a mighty 167 laps under his belt, there was an all-too-familiar sight of the McLaren being loaded onto a recovery truck as it broke down three times at the Circuit de Catalunya.
Red Bull also caused another red flag in the afternoon as Max Verstappen lost yet more precious track time when the RB14 came to a grinding halt at Turn 1.
Vandoorne only managed 38 laps on a grim day for McLaren and their MCL33, which suffered two power shutdowns in the morning session and a hydraulics issue after the lunch break. There were also reports of the bodywork overheating due to its proximity to the exhaust.
Verstappen, meanwhile, was able to pump in 114 laps and the third quickest time of the day before his afternoon came to a sudden stop. Red Bull were able to get him back out, though, for a final 15-minute flurry of action.
There was also something amiss at Toro Rosso and Haas respectively with fifth-placed Pierre Gasly and sixth-placed Kevin Magnussen also spending a large amount of time in the garage.
Gasly only added one installation lap in the afternoon as the screens stayed firmly in place outside the Toro Rosso garage, while the Haas VF-18 was hindered by a ERS problem which was fixed in time for the Dane to return to the track inside the final hour.
That’s the day finished 🏁
— Toro Rosso (@ToroRosso) March 6, 2018
Elsewhere, it was business as usual for Mercedes with Valtteri Bottas and Lewis Hamilton enjoying another productive on split-shift duties.
Bottas racked up 86 laps on his way to P2, two tenths off Vettel's Ferrari on the quicker soft tyres, while Hamilton steadily progressed up the leaderboard before settling for P4 and 88 more laps to his name.
As the Ferrari and Mercedes cars smashed through the 100-lap barrier, Marcus Ericsson became another centurion in the closing stages on a good day for the new-look Sauber, who announced Tatiana Calderon as their test driver shortly after the lunch break.
Force India's Sergio Perez was able to push into 90-lap territory and P10 in the standings following an early spin at Turn 4.
Carlos Sainz and Lance Stroll were the other afternoon drivers at Renault and Williams respectively, with the latter propping up the day five timesheet after replacing Sergey Sirotkin, who between them took the FW41 over the 100-lap mark.
1) Vettel, Ferrari, 168 laps, Medium tyres – 1:20.396
2) Bottas, Mercedes, 86 laps, Soft tyres – 1:20.596
3) Verstappen, Red Bull, 127 laps, Medium tyres – 1:20.649
4) Hamilton, Mercedes, 88 laps, Soft tyres – 1:20.808
5) Gasly, Toro Rosso, 54 laps, Soft tyres – 1:20.973
6) Magnussen, Haas, 93 laps, Soft tyres – 1:21.298
7) Hulkenberg, Renault, 48 laps, Medium tyres – 1:21.432
8) Sainz, Renault, 91 laps, Soft tyres, 1:21.455
9) Sirotkin, Williams, 42 laps, Soft tyres – 1:21.588
10) Perez, Force India, 87 laps, Soft tyres – 1:21.643
11) Ericsson, Sauber, 118 laps, Supersoft tyres – 1:21706
12) Vandoorne, McLaren, 38 laps, Supersoft tyres – 1:21.946
13) Stroll, Williams, 83 laps, Soft tyres – 1:22.937