Williams set the fastest time of the second day of the final pre-season test in Barcelona this week as new team Haas continued to struggle with another reliability issue.
After finishing second to Nico Rosberg on day one, Valtteri Bottas went one better on Wednesday with a quick lap on the super-soft tyres. His time of 1:23.261 was actually slower than his best effort on Tuesday, but it was still enough to top the times as Mercedes' pace dropped by 0.6s on the second day.
Mercedes is splitting all four days of this week's test between its two drivers, and on Wednesday it was Rosberg's turn to complete a race simulation in the afternoon while Hamilton went in search of a quick qualifying-style lap on soft tyres in the morning. Rosberg set a benchmark time of 1:23.022 on the soft tyres on Tuesday and Hamilton ended up exactly 0.6s short of this team-mate on his attempt on Wednesday. Varying track conditions or different fuel loads may have accounted for some of the gap, but Hamilton admitted he was still not 100 percent comfortable with the new W07.
"To get to light fuel is always an exciting feeling, but it's always new when you get back to pushing on a single lap," he said. "The car is in a different ballpark at the moment, but not in the right one, so that's what we've got to work on to get right for tomorrow.
"At the moment I'm just getting acquainted with it; it's like the first date."
Kevin Magnussen's relationship with his new Renault seems to be improving, however, as he set a 1:23.933 on his final day of testing ahead of the first race in Melbourne. The time was set on super-softs and is the best lap recorded by the RS16 in testing so far. However, when compared with the laps of rival teams on the same tyre compounds, the Renault is still lacking. Jolyon Palmer will take over driving duties for the remaining two days.
After concerns about reliability on Tuesday, Ferrari answered its critics with 144 laps of the Circuit de Catalunya on Wednesday. Much like Mercedes in the first week of testing, Sebastian Vettel stuck to the medium compound tyre and aimed for consistency over longer runs. He finished the day with a best lap of 1:24.611, but more importantly a lot more confidence in the durability of the SF16-H.
"I think we are on our plan," he said. "We have had some days where we would have liked to run a bit more but that is what the test is for. We are pretty happy with where we are."
At the other end of the pit lane, Ferrari engine customer Haas was not having such a smooth day. On Tuesday a fuel sensor issue stopped Esteban Gutierrez after 23 laps and on Wednesday a problem with the turbo limited him to just one lap at the wheel of the VF-16. It was the worst day of the team's short testing programme so far, but Gene Haas said problems are to be expected in the first weeks of testing.
"The past two days have been very frustrating," the team owner said. "We had an especially good week last week, but this is more what a typical normal week would be.
"I don't really have an explanation of why we're experiencing these problems now. But talking to others I think it's pretty typical you lose a day here and there because something doesn't go quite right, and that is what we've had the last two days."
Rival teams made full use of the good track conditions, with McLaren managing 121 laps, Red Bull 135 laps, Toro Rosso 166 laps and Force India 128 laps. McLaren continued to run its updated Honda power unit without major issue, although the team is still playing down expectations ahead of the first race.
Manor and Sauber failed to reach the 100 lap milestone, with Marcus Ericsson causing a late red flag when the new C35 stopped on track.
Times
1. Valtteri Bottas - Williams - 1:23.261 - 107 laps
2. Lewis Hamilton - Mercedes - 1:23.622 - 73 laps (morning)
3. Kevin Magnussen - Renault - 1:23.933 - 126 laps
4. Sebastian Vettel - Ferrari - 1:24.611 - 151 laps
5. Jenson Button - McLaren - 1:25.183 - 121 laps
6. Daniel Ricciardo - Red Bull - 1:25.235 - 135 laps
7. Carlos Sainz - Toro Rosso - 1:25.300 - 166 laps
8. Sergio Perez - Force India - 1:25.593 - 128 laps
9. Nico Rosberg - Mercedes - 1:26.298 - 91 laps (afternoon)
10. Pascal Wehrlein - Manor - 1:27.064 - 79 laps
11. Marcus Ericsson - Sauber - 1:27.487 - 55 laps
12. Esteban Gutierrez - Haas - No time - 1 lap