McLaren's Lewis Hamilton remained on top in second practice for the Chinese Grand Prix, as his first quick time remained unbeaten all afternoon.
His title rival Felipe Massa was only sixth fastest, with the two Renaults, Toyota's Jarno Trulli and Red Bull's Mark Webber splitting the championship rivals.
Hamilton came out for a short run as soon as the session began and set an early 1:35.750 before pitting.
That put him a full second clear of the pack at the time, and unusually his first time stood as the benchmark throughout the session.
Indeed few drivers managed to improve on their early laps until the final minutes, and the title contenders in particular struggled to gain any time when they tried the softer tyres.
Trulli fared better on the softs and spent much of the session in second until being pushed back to fourth when Fernando Alonso and Nelson Piquet jumped up the order late on.
Massa was edged right back to 10th as others improved in the closing minutes, but salvaged sixth behind Webber with his final lap, despite running slightly wide at the last corner.
Bourdais took seventh, despite ending the session off the road. The Frenchman had a series of adventures at Turn 2 - twice running wide over the grass strip there before eventually spinning into the gravel trap with ten minutes to go.
His teammate Sebastian Vettel also explored the circuit's limits, running very wide at both Turn 2 and on the exit of the fast Turn 13.
Webber was another driver to run wide over the Turn 2 run-off, while Turn 12 continued to cause problems too, with both Kimi Raikkonen and Piquet spinning there.
Raikkonen ended the session in eighth, with Nick Heidfeld (BMW) and Nico Rosberg (Williams) completing the top ten, the latter having held fourth for much of the session.
Pos Driver Team Time Laps
1. Hamilton McLaren-Mercedes (B) 1:35.750 33
2. Alonso Renault (B) 1:36.024 + 0.274 36
3. Piquet Renault (B) 1:36.094 + 0.344 38
4. Trulli Toyota (B) 1:36.159 + 0.409 32
5. Webber Red Bull-Renault (B) 1:36.375 + 0.625 38
6. Massa Ferrari (B) 1:36.480 + 0.730 31
7. Bourdais Toro Rosso-Ferrari (B) 1:36.529 + 0.779 32
8. Raikkonen Ferrari (B) 1:36.542 + 0.792 34
9. Heidfeld BMW Sauber (B) 1:36.553 + 0.803 38
10. Rosberg Williams-Toyota (B) 1:36.556 + 0.806 33
11. Glock Toyota (B) 1:36.615 + 0.865 33
12. Kubica BMW Sauber (B) 1:36.775 + 1.025 37
13. Kovalainen McLaren-Mercedes (B) 1:36.797 + 1.047 33
14. Coulthard Red Bull-Renault (B) 1:36.808 + 1.058 36
15. Vettel Toro Rosso-Ferrari (B) 1:36.925 + 1.175 38
16. Nakajima Williams-Toyota (B) 1:36.975 + 1.225 31
17. Fisichella Force India-Ferrari (B) 1:37.473 + 1.723 38
18. Sutil Force India-Ferrari (B) 1:37.617 + 1.867 33
19. Button Honda (B) 1:37.800 + 2.050 37
20. Barrichello Honda (B) 1:37.904 + 2.154 36
All Timing Unofficial