MONTMELO, Spain -- Valtteri Bottas put Mercedes top on the second morning of testing, though McLaren's Stoffel Vandoorne and Ferrari's Sebastian Vettel were close behind.
A bitterly cold start to the day meant early running was minimal -- temperatures only crept above one degrees Celsius after a few quiet hours had passed. The improving conditions triggered a flurry of on-track activity as teams set about making up for lost time.
Bottas led the leaderboard in both the mileage and timing stakes at the mid-way point in the Mercedes W09 that is expected to mount a strong challenge for a record-equalling fifth consecutive championship this season. Vandoorne put his papaya orange McLaren into second place with a run on Pirelli's new hyper-soft tyre -- 0.05s off Bottas' run on softs, though reading too much into times and performance gaps at this stage of testing is largely irrelevant.
Bottas was due to hand the Mercedes over to Hamilton in the afternoon, but with track time limited by the weather the team decided not to switch it drivers and stick with Bottas.
Vettel was third after his first morning behind the wheel of the Ferrari. After an impressive opening day, Renault was limited to just 20 laps with Carlos Sainz, though Renault chief Cyril Abiteboul told the media there was no issue other than ensuring the team ran in optimal conditions in the afternoon, when temperatures improved further.
Williams' Sergey Sirotkin got his first proper laps of the Circuit de Catalunya, having completed a short stint in the cold and wet conditions which hampered the teams on Monday evening. Force India returned to the circuit after a very frustrating opening day and saw Esteban Ocon match the tally set by development driver Nikita Mazepin on Monday before a session-ending spin.
Reigning Formula 2 champion Charles Leclerc enjoyed a productive morning for Sauber, accumulating 42 laps by lunch.
Haas and Red Bull saw very limited action. Kevin Magnussen and Max Verstappen completed just a handful of installation laps. The Red Bull returned to the track in the early afternoon once a fuel leak had been fixed.
Times at 13:00
1. Bottas, Mercedes, 1:20.270, 43 laps
2. Vandoorne, McLaren, 1:20.325, 32 laps
3. Vettel, Ferrari, 1:21.010, 33 laps
4. Sainz, Renault, 1:22.125, 20 laps
5. Sirotkin, Williams, 1:22.588, 40 laps
6. Ocon, Force India, 1:22.907, 21 laps
7. Gasly, Toro Rosso, 1:24.667, 23 laps
8. Leclerc, Sauber, 1:23.917, 42 laps
9. Magnussen, Haas, 1.42.276, 6 laps
10. Verstappen, Red Bull, No time, 3 laps