Valtteri Bottas put Mercedes top on the second day of the second pre-season Formula 1 test at the Circuit de Barcelona-Catalunya with the fastest lap of testing so far, a 1:19.310, four-tenths quicker than he managed during the opening test last week.
The Mercedes driver set his time during the morning session, before handing the car over to team-mate Lewis Hamilton for the afternoon's running.
With Hamilton focusing on longer runs, and using the soft compared to the supersoft, he finished sixth overall, 1.392 down on Bottas.
Felipe Massa once displayed Williams' potential by going second quickest, just 0.110 seconds slower than Bottas, albeit on the quicker ultrasoft tyre.
Kimi Räikkönen was third fastest for Ferrari, but the team's day didn't quite go to plan following a lengthy stoppage before lunch due to a fluid systems check prior to lunch.
In the afternoon, Räikkönen spun through Turn 3 before coming to a rest against the tyre wall. The contact caused minor damage and he failed to return to the track after that.
Räikkönen's off caused the first of three red flags, with the second coming when Max Verstappen, fourth quickest, stopped at Turn 13 in the Red Bull RB13.
The session was extended by five minutes, but that proved unnecessary as a stoppage for Marcus Ericsson at Turn 8 with five minutes to go ended the day's running.
Lance Stroll was fifth fastest for Williams as the Canadian rookie enjoyed a much better day than his previous outings, as he finished ahead of Hamilton, Sergio Pérez and Carlos Sainz Jr.
Haas' Romain Grosjean took 10th, ahead of Sauber's Pascal Wehrlein, with both having drama-free days in their respective cars.
Fernando Alonso only managed 46 laps – the fewest for any of the 10 teams, as he placed a lowly 12th, ahead of only Ericsson and Jolyon Palmer, who both drove solely in the afternoon session.
| Pos | Driver | Team | Time | Gap | Tyre | Laps |
| 1 |  Valtteri Bottas |
Mercedes | 1:19.310 |  |
70 | |
| 2 |  Felipe Massa |
Williams | 1:19.420 | 0.110 |  |
63 |
| 3 | Kimi Raikkonen |
Ferrari | 1:20.406 | 1.096 |  |
53 |
| 4 |  Max Verstappen |
Red Bull | 1:20.432 | 1.122 | |
101 |
| 5 |  Lance Stroll |
Williams | 1:20.579 | 1.269 | |
59 |
| 6 |  Lewis Hamilton |
Mercedes | 1:20.702 | 1.392 | |
79 |
| 7 |  Nico Hulkenberg |
Renault | 1:21.213 | 1.903 | |
61 |
| 8 |  Sergio Perez |
Force India | 1:21.297 | 1.987 | |
100 |
| 9 |  Carlos Sainz |
Toro Rosso | 1:21.872 | 2.562 | |
92 |
| 10 |  Romain Grosjean |
Haas | 1:21.887 | 2.577 | |
96 |
| 11 | Pascal Wehrlein |
Sauber | 1:23.000 | 3.690 | |
59 |
| 12 | Fernando Alonso |
McLaren | 1:23.041 | 3.731 | |
46 |
| 13 |  Marcus Ericsson |
Sauber | 1:23.384 | 4.074 | |
47 |
| 14 | Jolyon Palmer |
Renault | 1:24.774 | 5.464 | |
29 |
