Valtteri Bottas topped the timesheet on the first day of the second in-season test conducted at the Circuit de Catalunya in Barcelona.
The Mercedes driver was comfortably ahead of the field, putting 94 laps under his belt and clocking in with a 1m15.511 that was 1.8s faster than Ferrari's Charles Leclerc.
Toro Rosso's Daniil Kvyat concluded the day third fastest, edging Renault's Nico Hulkenberg and McLaren's Carlos Sainz.
| Pos | Driver | Team | Time | Laps |
|---|---|---|---|---|
| 1 | Bottas | Mercedes | 1:15.511 | 131 |
| 2 | Leclerc | Ferrari | 1:16.933 | 132 |
| 3 | Kvyat | Toro Rosso | 1:17.679 | 121 |
| 4 | Hulkenberg | Renault | 1:18.051 | 68 |
| 5 | Gasly | Red Bull | 1:18.140 | 118 |
| 6 | Sainz | McLaren | 1:18.263 | 64 |
| 7 | Fittipaldi | Haas | 1:18.326 | 103 |
| 8 | Yelloly | Racing Point | 1:18.361 | 111 |
| 9 | Vettel | Ferrari (Pirelli) | 1:18.425 | 133 |
| 10 | Norris | McLaren | 1:18.567 | 44 |
| 11 | Perez | Racing Point (Pirelli) | 1:19.719 | 118 |
| 12 | Ilott | Alfa Romeo | 1:19.819 | 41 |
| 13 | Latifi | Williams | 1:20.670 | 134 |
Callum Ilott and Nick Yelloly, running respectively for Alfa Romeo and Racing Point, were Tuesday's unfamiliar faces while the rest of the field, save for Haas' Pietro Fittipaldi and Williams' Nicholas Latifi, was comprised of the teams' usual drivers.
However, Ferrari and Racing Point fielded second cars for Pirelli's tyre development programme, with Sebastian Vettel and Sergio Perez on duty.
The morning unfolded with out any major drama with Mercedes' Valtteri Bottas clocking before the lunch break with the fastest lap using the C3 tyre, which was last weekend's designated soft compound.
The Finn's 1m16.525s lap eclipsed the hard-shod Ferrari of Charles Leclerc by 0.797 seconds.
The gap between the two front-runners and third-placed man Carlos Sainz was over a second, with the McLaren driver just edging Red Bull's Pierre Gasly who put in the most laps in the morning session while Vettel rounded off the top five.
In the afternoon, Bottas picked up where he had left off, bolting on a set of C5 tyres - a compound two steps softer than the rubber used in Sunday's race - to a time of 1m15.511s, just 0.105 slwoer the his pole position in Spain.
Leclerc also improved his personal best, although he did it late in the day with a charge using the C2 tyre.
Kvyat was another driver to put in a flyer in the closing stages of the session, an effort that yielded P3 on the timesheet.
Two drivers saw their day of work grind to a premature halt in the afternoon. Rookie Ilott crashed heavily at the Circuit de Catalunya's fast turn 3 right-hander, escaping injury but damaging his car beyond repair.
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