Michael Schumacher ended the first day of practice for the Chinese Grand Prix on top of the timesheets.
After rain restricted the number of laps completed in the morning, every team opted for an intense schedule during the second 90-minute session.
Morning pacesetter Lewis Hamilton picked up where he left off early on, hitting top spot after just eight minutes while on a six-lap run on medium Pirellis.
With everyone opting for primes for their first serious runs, Hamilton's time was 0.134s faster than Schumacher, with Red Bull Racing's Sebastian Vettel two-tenths further back.
Hamilton and the Mercedes driver continued on mediums on their second run, while Sauber driver Kamui Kobayashi jumped up to third place with a lap within a tenth-and-a-half off Hamilton on the half-hour mark. A few minutes later, the Japanese survived a lurid slide off the track after being caught out while pushing too hard.
Vettel was the first of the frontrunners to set a time on the soft compound tire, lapping a quarter of a second quicker than Hamilton on the first flier of his second run and subsequently improving by another four tenths of a second.
Teammate Mark Webber, running the latest-spec exhaust compared to the early specification used in the first part of pre-season testing that Vettel ran, slotted in just under three-tenths behind his teammate not long before the halfway point of the session.
While the Red Bulls had taken three laps to get the peak performance out of their soft tires, both Schumacher and Hamilton, who shortly after headed out on their fresh soft rubber, extracted the performance from their tires immediately.
Schumacher posted his best time, a 1m35.973s, on his first flier, but Hamilton looked set to outpace him after setting the best time of all in sectors one and two before losing his advantage, and another 0.172s, in the final sector.
Neither Nico Rosberg in the second Mercedes, nor Jenson Button in the second McLaren, were able to match the pace of their teammates, ending up fifth and sixth ahead of Kobayashi, whose earlier lap on prime rubber was enough for seventh overall.
Force India driver Paul di Resta ended up eighth fastest, within a second of the outright pace and a couple of tenths ahead of teammate Nico Hulkenberg, with Alonso, who couldn't get the maximum out of his soft tires on his first flying lap, just behind.
Several drivers had offs during the session. Both di Resta and Caterham driver Vitaly Petrov suffered spins at the final corner after running wide at the exit and losing it on the damp runoff, but the biggest moment of the day was provided by Marussia driver Timo Glock.
The German appeared to lose his front wing under braking for Turn 1, locking up and clattering through the gravel trap and ending up against the barrier. The team was uncertain as to the cause of the off, but Glock's initial concern that he had hurt his hands soon abated.
Pos Driver Team Time Laps
1. Michael Schumacher Mercedes 1m35.973 32
2. Lewis Hamilton McLaren-Mercedes 1m36.145s + 0.172 29
3. Sebastian Vettel Red Bull-Renault 1m36.160s + 0.187 26
4. Mark Webber Red Bull-Renault 1m36.433s + 0.460 23
5. Nico Rosberg Mercedes 1m36.617s + 0.644 30
6. Jenson Button McLaren-Mercedes 1m36.711s + 0.738 27
7. Kamui Kobayashi Sauber-Ferrari 1m36.956s + 0.983 28
8. Paul di Resta Force India-Mercedes 1m36.966s + 0.993 30
9. Nico Hulkenberg Force India-Mercedes 1m37.191s + 1.218 30
10. Fernando Alonso Ferrari 1m37.316s + 1.343 32
11. Sergio Perez Sauber-Ferrari 1m37.417s + 1.444 22
12. Daniel Ricciardo Toro Rosso-Ferrari 1m37.616s + 1.643 33
13. Kimi Raikkonen Lotus-Renault 1m37.836s + 1.863 30
14. Jean-Eric Vergne Toro Rosso-Ferrari 1m37.930s + 1.957 31
15. Romain Grosjean Lotus-Renault 1m37.972s + 1.999 25
16. Pastor Maldonado Williams-Renault 1m38.176s + 2.203 34
17. Felipe Massa Ferrari 1m38.293s + 2.320 30
18. Bruno Senna Williams-Renault 1m38.783s + 2.810 37
19. Heikki Kovalainen Caterham-Renault 1m38.990s + 3.017 36
20. Vitaly Petrov Caterham-Renault 1m39.346s + 3.373 19
21. Timo Glock Marussia-Cosworth 1m39.651s + 3.678 15
22. Pedro de la Rosa HRT-Cosworth 1m40.343s + 4.370 24
23. Charles Pic Marussia-Cosworth 1m40.753s + 4.780 30
All Timing Unofficial