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 mid-way point in the Mercedes W09 expected to mount a strong challenge for a record-equalling fifth consecutive championship this season.