Nico Rosberg ensured that a 2011-spec car topped the timesheets for the second consecutive day at Jerez, resetting the fastest lap of the week so far.
The German replaced countryman Michael Schumacher behind the wheel of the lone W02 for what was to be the final day of Mercedes' initial run-out, which largely consisted of the Brackley team evaluating the latest range of Pirelli tyres.
Having shaken off the winter rust on the opening day on Tuesday, Rosberg completed 118 laps which also allowed the team to put more mileage on 2012 development items on the car. In all, Mercedes completed 1541km in its three days, gathering comprehensive knowledge of the new tyres with varying set-ups and fuel loads before its 2012 car, the W03, makes its public test debut in Barcelona.
“I'm happy with the testing that we have achieved here in Jerez, and we learned a lot about the Pirelli tyres and a few other things for the new car," Rosberg confirmed, "It seems that the tyres are closer performance-wise this year, with the rear tyres also looking a bit stronger. Pirelli have done a good job so far.
"You can't really compare the lap times with other teams, but it was interesting to learn a lot with our 2011 car. Now I'm really looking forward to the two Barcelona tests with our new Silver Arrow.”
Rosberg's fastest lap beat Schumacher's Wednesday best by almost a second and proved to be eight-tenths quicker than anyone else managed on the day.
Second fastest was Lotus' 'other' returnee, Romain Grosjean, who started the day by vaulting to the top of the times, and ended it by running out of fuel on his final outing.
The Frenchman mirrored new team-mate Kimi Raikkonen by remaining at the sharp end of the times for the entire day, eventually edging out both reigning world champion Sebastian Vettel and predecessor Lewis Hamilton by eight-tenths and one second respectively. It is thought that Grosjean was attempting a late flying run when his E20 ran dry, stranding him on the circuit and bringing out the red flags which eventually turned to the chequer and ended the day on a quiet note.
Vettel got his first taste of the new RB8 after replacing Mark Webber behind, and enjoyed a largely trouble-free run once temperatures had risen high enough to make running meaningful.