Kamui Kobayashi topped the times for Sauber during Friday morning's rain-drenched opening practice session for Sunday's Belgian Grand Prix.
The 25-year-old Japanese was one of a handful of drivers to complete more than ten full laps as most teams elected not to spend much time on track due to the amount of rain falling on the Spa Francorchamps circuit.
Kobayashi went fastest with half an hour remaining before improving on his time nine minutes before the end of the session, clocking a lap of the historic circuit in one minute 11.389 seconds.
Venezuelan Pastor Maldonado of Williams was just 0.5 seconds slower in second followed by Toro Rosso drivers Australian Daniel Ricciardo and Frenchman Jean-Eric Vergne who were third and fourth-quickest respectively. Red Bull driver Australian Mark Webber, fifth quickest, was the fastest of the title contenders followed by Mexican Sergio Perez in the second Sauber.
German Nico Rosberg of Mercedes was seventh fastest followed by Finn Valtteri Bottas in the other Williams.
German Michael Schumacher, who celebrates his 300th Grand Prix this weekend was ninth fastest in the other Mercedes followed by his compatriot Sebastian Vettel who completed the top ten in the second Red Bull.
The times of the first practice:
.1. Kamui Kobayashi (JPN/Sauber C31) 2:11.389 .2. Pastor Maldonado (VEN/Williams FW34) 2:11.941 .3. Daniel Ricciardo (AUS/Toro Rosso STR7) 2:12.004 .4. Jean-Eric Vergne (FRA/Toro Rosso STR7) 2:12.824 .5. Mark Webber (AUS/Reb Bull RB8) 2:13.191 .6. Sergio Pérez (MEX/Sauber C31) 2:13.861 .7. Nico Rosberg (GER/Mercedes F1 W03) 2:14.210 .8. Valtteri Bottas (FIN/Williams FW34) 2:14.660 .9. Sebastian Vettel (GER/Red Bull RB8) 2:14.860 10. Michael Schumacher (GER/Mercedes F1 W03) 2:15.402 11. Paul di Resta (FRA/Force India VJM05) 2:15.812 12. Timo Glock (GER/Marussia MR01) 2:16.409 13. Niko Hülkenberg (GER/Force India VJM05) 2:16.786 14. Vitaly Petrov (RUS/Caterhan CT01) 2:16.788 15. Lewis Hamilton (GBR/McLaren MP4-27) 2:16.827 16 Jenson Button (GBR/McLaren MP4-27) 2:16.861 17. Charles Pic (FRA/Marussia MR01) 2:17.519 18. Heikki Kovalainen (FIN/Caterham CT01) 2:18.199 19. Pedro de la Rosa (ESP/HRT 112) 2:19.546 20. Dani Clos (ESP/HRT 112) 2:19.689 21. Romain Grosjean (FRA/Lotus E20) 2:38.701 22. Fernando Alonso (ESP/Ferrari F2012) 2:40.749 23. Kimi Raikkonen (FIN/Lotus E20) 2:46.580 24. Felipe Massa (BRA/Ferrari F2012) n.t.