Kimi Raikkonen posted the quickest time in the first morning of testing in 2012 as the returning 2007 world champion set the pace in the new Lotus E20.
The Finn responded to the hype surrounding his return with four fast stints, and occupied the top spot on the timesheets from the minute he first left the garage.
His fastest time so far, a 1m19.670s, set on his third run using medium Pirelli tyres, was faster than any testing laps at the Spanish track throughout 2011.
Lotus confirmed that the team's programme was simply to put miles on the new car and to give Raikkonen as much time as was possible to get used to this year's Pirelli compounds. By 13:00 local time, the Finn had completed 50 laps.
Paul di Resta was second fastest in the new Force India, having spent much of the morning doing intensive evaluation of the VJM05 which sported a large pylon mounted on the roll-bar.
Nico Rosberg was third fastest, driving a 2011 Mercedes W02 with some modifications. Having initially worked on calibration and installation, the German quickly upped the ante and by lunchtime had worked down to a 1m20.219s lap on Pirelli's soft rubber.
Daniel Ricciardo was fourth fastest in the Scuderia Toro Rosso having completed a trouble-free 40 laps so far in the STR7, which was revealed to the world at Jerez on Monday evening.
Mark Webber completed just eight laps in the new Red Bull RB8 but finished as fifth quickest.
Kamui Kobayashi was sixth fastest in the Sauber C31. The Japanese driver's only problem was the loss of a small piece of the rear brake duct on his initial run, but the team quickly resolved the issue.
Jenson Button was seventh for McLaren, which took its time working through systems checks and installation runs. Meanwhile, Felipe Massa was eighth quickest for Ferrari. The Brazilian focussed on data gathering in the F2012 - which was also carrying a tall pillar on its roll-hoop.
Heikki Kovalainen completed 18 laps by lunchtime for Caterham - the Finn having achieved a best of 1m23.1748, ahead of Pastor Maldonado in the new Williams-Renault. The FW34 was also revealed to the world in a roll-out just before the start of the test this morning.
Pedro de la Rosa completed the order in last year's HRT.
Pos Driver Team Time Laps 1. Kimi Raikkonen Lotus-Renault 1m19.670s 50
2. Paul di Resta Force India-Mercedes 1m19.772s 52
3. Nico Rosberg Mercedes 1m20.219s 56
4. Daniel Ricciardo Toro Rosso-Ferrari 1m20.694s 40
5. Mark Webber Red Bull-Renault 1m21.474s 8
6. Kamui Kobayashi Sauber-Ferrari 1m21.534s 29
7. Jenson Button McLaren-Mercedes 1m22.402s 22
8. Felipe Massa Ferrari 1m23.056s 51
9. Heikki Kovalainen Caterham-Renault 1m23.178s 32
10. Pastor Maldonado Williams-Renault 1m23.371s 23
11. Pedro de la Rosa HRT-Cosworth 1m24.322s 16
All Timing Unofficial