Antonio Giovinazzi knocked Pierre Gasly off top spot in the morning session, but it was McLaren’s young British hope, Lando Norris, who finished an eventful day top of the pile following a late surge in the afternoon.
Norris posted a 1:17.709 on what Pirelli confirmed as the C4 compound, pipping Gasly once again by a mere 0.006 seconds.
That is the fourth quickest time we have seen of the entire testing period so far, whilst rounding off the top three was Lance Stroll in the Racing Point car which is finally showing signs of life.
But, with lap times still to be taken with a pinch of salt, the most predominant talking point is the Ferrari and Mercedes cars have both spent a large portion of the day stuck in the garage.
The issues began to creep in early as Charles Leclerc’s morning run was restricted to just 29 laps because of extensive checks to the SF90’s cooling system.
— Scuderia Ferrari (@ScuderiaFerrari) February 26, 2019
However, it did appear to be business as usual in the afternoon for the Scuderia with Sebastian Vettel racking up 78 laps before finishing P4 on the timesheet.
Mercedes, meanwhile, came armed to the second test with a new-look W10 sporting what is rumoured to be a Melbourne-spec upgrade package.
The car featured a new front wing and nose, revised bargeboards, chassis fins and T-wing, as well as a new floor and more compact sidepods.
The data collection began well enough as Lewis Hamilton was able to post up 83 laps, but the roles with Ferrari reversed as the W10 then came to a grinding halt on Valtteri Bottas’ first lap of the afternoon session.
Mercedes later confirmed the stoppage was because of an oil pressure problem and the power unit was changed as a result.
UPDATE: @ValtteriBottas stopped on track with an oil pressure problem.
— Mercedes-AMG F1 (@MercedesAMGF1) February 26, 2019
Any PU change made in pre-season has no ramifications for the campaign ahead.
But it did mean that both the big two lost out on some valuable track time for the first time in this pre-season testing period.
Back at the top of the timesheet, a certain Fernando Alonso was an interested spectator in the paddock and he saw Norris stick the MCL34 into P1 late into the day.
— Circuit de Barcelona-Catalunya (@Circuitcat_eng) February 26, 2019
But the session would end on a sour note for the teenager as he forced a red flag by stopping on track.
It was the second incident of the day for Norris, who became beached at Turn 3 in the morning session because of a loss of hydraulic pressure.
There were no such issues for the likes of Haas and Renault – victims of various stoppages in the first test – as they both comfortably surpassed the 100-lap mark at the Circuit de Catalunya.
The same important milestone was reached by the lowly Williams team, who completed just 88 laps in the first test.
George Russell added 115 laps to their total on this day alone.
The second day of the second pre-season test will begin at 0900 local time on Wednesday.
Day One timesheet:
1 Lando Norris McLaren 80 laps 1:17.709 C4
2 Pierre Gasly Red Bull 136 laps 1:17.715 C3
3 Lance Stroll Racing Point 82 laps 1:17.824 C4
4 Sebastian Vettel Ferrari 81 laps 1:17.925 C3
5 Antonio Giovinazzi Alfa Romeo 99 laps 1:18.589 C4
6 Alexander Albon Toro Rosso 103 laps 1:18.649 C4
7 Charles Leclerc Ferrari 29 laps 1:18.651 C3
8 Kevin Magnussen Haas 131 laps 1:18.769 C4
9 George Russell Williams 119 laps 1:19.662 C5
10 Daniel Ricciardo Renault 77 laps 1:20.107 C2
11 Valtteri Bottas Mercedes 7 laps 1:20.167 C2
12 Lewis Hamilton Mercedes 83 laps 1:20.332 C2
13 Nico Hulkenberg Renault 80 laps 1:20.348 C3
C1 = Hardest tyre C5 = Softest tyre