While Lewis Hamilton set the pace at lunch on Day One at Barcelona, his former team-mate Jenson Button once again struggled in his MP4-30.
Hamilton dominated the timesheets on Thursday morning at the Spanish track, hitting the front early on.
Clocking a 1:24.881 on the medium Pirelli tyres, he was 0.882s up on Williams' Felipe Massa when a constant drizzle began to fall in the hour before lunch.
As such no one was able to challenge his time and Hamilton claimed the early P1.
Massa remained second with Daniil Kvyat third quickest in his RB11, 1.066s off the pace.
It was a stuttering start to the morning for the Russian racer as he brought out the morning's only red flag when he stopped while exiting the pits just minutes into testing.
He was, however, soon up and running and amassed 45 laps, second busiest behind Hamilton.
Romain Grosjean was fourth quickest in the Lotus ahead of Marcus Ericsson and Kimi Raikkonen.
Carlos Sainz Jr and Jenson Button completed the timesheets with the latter covering just seven laps as McLaren once again spent more time in the garage than on the track.
Button's only timed lap was a 1:31.479.
01 Lewis Hamilton Mercedes 1:24.881 48 laps
02 Felipe Massa Williams 1:25.763 0.882 45 laps
03 Daniil Kvyat Red Bull 1:25.947 1.066 34 laps
04 Romain Grosjean Lotus 1:27.079 2.198 33 laps
05 Marcus Ericsson Sauber 1:27.802 2.921 33 laps
06 Kimi Raikkonen Ferrari 1:27.813 2.932 29 laps
07 Carlos Sainz Jr Toro Rosso 1:27.866 2.985 28 laps
08 Jenson Button McLaren 1:31.479 6.598 7 laps