Nico Rosberg emerged with the quickest time as the second pre-season test ahead of the 2013 F1 season kicked off at Catalunya.
On another somewhat truncated day for his Mercedes team, Rosberg was able to edge Kimi Raikkonen out of top spot in the latter stages of the session – where the top times were ultimately posted.
Rosberg had earlier lost time when work on the gearbox on his F1 W04 took longer than expected, meaning much of his running came during the afternoon session.
Making use of Pirelli's medium compound tyre in the final 20 minutes, Rosberg posted a quickest time of 1min 22.616secs which was good enough to leave him just 0.007secs clear of Raikkonen's Lotus after the Finn proved to be unable to beat the Mercedes on his best lap of the session.
“We had a mixed day today with some laps lost this morning,” Rosberg admitted. “However we were able to work through a good programme this afternoon and, of course, it's always nice to be quickest at the end of the day.
“In general, I feel happy and comfortable in the car and it feels better than the last time we were here at this track. There is still some work to be done on tyre degradation and our programme this afternoon was helpful in understanding that.”
Like Rosberg, Raikkonen also suffered his fair share of issues, logging fewer laps than anyone else as the team worked on issues with the data logger on his car that meant he spent time in the garage.
Despite that however, the team was pleased with the results from the day as the Enstone-based squad set about building on its solid performance at Jerez last week.
“It's been a positive debut for the second chassis here in Barcelona,” trackside operations director Alan Permane said. “Kimi was happy with where the car started the day, and the setup changes we've made have been positive.
"We had a few issues on the electronics side with the telemetry data-logging and this has cost us track time as well as the ability to conduct longer runs. Other than that, we've been able to take over from where we left off in Jerez so we're happy with that. All we need is more laps, which is our focus for tomorrow.”
Behind the top two, Fernando Alonso was third quickest for Ferrari as he got behind the wheel of the new F138 for the first time having elected to sit out the first session of the year at Jerez in favour of training away from the circuit.
Given his lack of time in the car, there was little surprise to see the Spaniard as the busiest man on track as he completed more than 20 laps more than anyone else – racking up 110 in total over the course of a busy day.
Like the men ahead, Alonso's best time came on the medium tyre and he was able to edge defending champion Sebastian Vettel out of the top three; Vettel having been the man to beat at lunchtime and having led the way for much of the afternoon.
On an encouraging day for Williams, Pastor Maldonado was just over a second off the pace in fifth place on the first day of running for the new FW35 with the Toro Rosso of Daniel Ricciardo rounding out the top six.
Sergio Perez was seventh for McLaren and just 0.020secs quicker than Paul di Resta's Force India and the Sauber of Esteban Gutierrez; the young Mexican brining out a red flag when he ran out of fuel on track.
In the battle at the back, Max Chilton took tenth for Marussia with Charles Pic eleventh for Caterham having brought out the second red flag of the day when he stopped with a mechanical problem that ended his session early.
“49 laps on the first day of the second test isn't the total we wanted,” the Frenchman said, “but we've still been able to complete quite a bit of today's program and with every lap I'm getting more and more comfortable in the car.
“In the morning session we ran through a similar program to the second day in Jerez last week, and we had planned more tyre work in the afternoon. When I went out for a stint after the lunch break I had a mechanical problem going into turn three and after we got the car back to the garage we found out it was a gearbox issue and that brought the day to an early end.
"We've already started work on the fix and I'm sure we'll be ready for tomorrow morning when we can get back to work.”
To see times from day one, CLICK HERE