Three days after claiming victory in the Austrian Grand Prix, Nico Rosberg ensured that Mercedes remained the team to beat in F1 testing, posting the best time of the two-day session to claim top spot on Wednesday.
The German began his day at the wheel in leisurely fashion, completing an aero test for the Brackley-based team at a pace nearly half a minute off the leading times from day one, but picked up speed after an hour-and-a-half, homing in on the benchmark held by Williams' Valtteri Bottas.
Although he remained second fastest to the Finn through the hour-long lunch break, a situation beyond his control due to the Mercedes needing attention for a gearbox glitch, Rosberg was straight back out when he resumed, initially chipping away at his 1m 10s time before taking advantage of an empty track to post a 1m 09.419s lap. He improved that to 1m 09.113s next time around, and the mark would remain unbeaten to the chequered flag nearly four hours later, despite both Rosberg and several rivals getting close to it on the supersoft Pirelli rubber.
Although there was no repeat of the heavy rain that wiped out Tuesday morning's session and prompted organisers to extend day one by a couple of hours, the occasional brief shower threatened to interrupt proceedings, but very little running was lost other than to a couple of red flags, brought about by Rosberg and Red Bull's Daniel Ricciardo both stopping in the pit-lane access roads.
The Australian was never a menace to Rosberg, languishing down the order and sitting out a long time after lunch while the team worked on his RB11. Although he moved up the order after getting back on track, and racked up in excess of 100 laps for the day, he remained over a half-second off the top five.
Rosberg's closest rival ultimately proved to be Esteban Gutierrez, who overcame both Antonio Fuoco's Tuesday crash and his own trip into the gravel during the morning session to push Ferrari to P2 late in the day. Like Ricciardo, the Mexican had spent a lot of the day at the wrong end of the timesheets as he worked his way through the Scuderia's programme, but was allowed his head in the final couple of hours, eventually improving to 1m 09.931s.
That pushed long-time pacesetter Bottas down to third spot, the Finn also notably completing fewer laps than his rivals as he failed to break 100 for the day. The Williams appeared to have good pace, but Bottas sat out a big chunk of the afternoon, and failed to lower the time he set in the early going.
Indeed, the Finn came under threat from F1 rookie Marco Wittmann who, having found his feet in the Toro Rosso during the morning, continued to pound around, not only to fourth spot on the timesheets, but also by far the highest lap total of the entire test, only stopping when his tally reached 158. The reigning DTM champion ended the day just a tenth shy of a place in the top three, and with Tuesday pacesetter Pascal Wehrlein in his mirrors.
Admittedly, Wehrlein was at the wheel of Force India's revised VJM08 this time around, rather than the Mercedes he took to top spot 24 hours ago, but that did not prevent the youngster from taking his turn at the top of the pile early on. The car briefly sported the new-look nose that Esteban Ocon had run on day one, but the test largely focused on other areas of the team's makeover package, with Wehrlein ultimately claiming fifth spot, just over a tenth slower than he managed on Tuesday.
McLaren also debuted a new nose on its MP4-30, the development part noticeably shorter than its predecessor. It remains to be seen how much of a role that played in Fernando Alonso's hold on a top four place through the middle of the day, but the Spaniard eventually wound up seventh fastest after Lotus' reserve Jolyon Palmer found time in the final hour to vault into P6. However, the Lotus then stopped on track with two minutes to go, bringing out a red flag that eventually morphed into the chequer.
Alonso ended the day just ahead of Ricciardo after the Australian's last-ditch improvement closed the gap between them to a matter of hundredths, but the main gain for McLaren would be the 104 laps Alonso racked up. Ricciardo's move did however leave Sauber's Felipe Nasr to bring up the rear, despite the Brazilian being in the same 1m 10s bracket as the five drivers immediately ahead of him.
Attention now turns to preparations for the British Grand Prix, which takes place at Silverstone in just over a week....