Points leader Fabio Leimer set the pace in Friday morning's free practice for the GP2 Series finale in Abu Dhabi, 0.158 seconds quicker than title rival Sam Bird.
Singapore race winner Jolyon Palmer set the pace in the early stages for Carlin with a 1m52.949s, until Bird hit the track and unleashed a 1m52.381s in his Russian Time entry.
His team-mate Tom Dillmann immediately leapt to second, just a tenth off the fastest time, while Racing Engineering's Leimer went third fastest on his first run, 0.235s off the leading pace.
Dani Clos then briefly jumped to the top of the times in his MP Motorsport machine, 0.026s ahead of Bird, as Alexander Rossi demoted Dillmann from third, with a lap 0.042s off the benchmark time.
On the second runs, Bird retook top spot with 1m51.924s, but was demoted by Leimer with a 1m51.766s that remained the best time until the end of the half-hour session.
Bird was slightly quicker on his final lap until he aborted it, setting up an intriguing scenario going into qualifying, in which the four points on offer for pole could prove crucial in the final reckoning. Bird is seven behind Leimer at present.
Clos dropped to third, ahead of Rossi.
James Calado, who has the slimmest of title hopes in his ART car, was fifth fastest. However, he is under investigation by the stewards after he tripped over sixth-fastest Dillmann and vented his feelings by running him wide off the track.
Jon Lancaster was seventh fastest, despite a spin. Simon Trummer and Daniel de Jong were also spinners during the session.
Of the other title contenders, Felipe Nasr was 10th and Stefano Coletti, who has been in freefall since the middle of the season, was 23rd and 2.2s off the pace.
All drivers used the white-walled medium compound Pirelli tyres, but will qualify later on Friday on the super-soft.
Pos Driver Team Time Gap 1. Fabio Leimer Racing Engineering 1m51.766s 2. Sam Bird Russian Time 1m51.924s +0.158s 3. Dani Clos MP 1m52.019s +0.253s 4. Alexander Rossi Caterham 1m52.061s +0.295s 5. James Calado ART 1m52.162s +0.396s 6. Tom Dillmann Russian Time 1m52.175s +0.409s 7. Jon Lancaster Hilmer 1m52.543s +0.777s 8. Stephane Richelmi DAMS 1m52.573s +0.807s 9. Johnny Cecotto Jr Arden 1m52.583s +0.817s 10. Felipe Nasr Carlin 1m52.697s +0.931s 11. Rene Binder Lazarus 1m52.709s +0.943s 12. Marcus Ericsson DAMS 1m52.801s +1.035s 13. Jolyon Palmer Carlin 1m52.822s +1.056s 14. Nathanael Berthon Trident 1m52.853s +1.087s 15. Jake Rosenzweig Addax 1m52.870s +1.104s 16. Julian Leal Racing Engineering 1m52.973s +1.207s 17. Sergio Canamasas Caterham 1m53.225s +1.459s 18. Simon Trummer Rapax 1m53.383s +1.617s 19. Daniel Abt ART 1m53.472s +1.706s 20. Rio Haryanto Addax 1m53.552s +1.786s 21. Adrian Quaife-Hobbs Hilmer 1m53.638s +1.872s 22. Daniel de Jong MP 1m53.750s +1.984s 23. Stefano Coletti Rapax 1m53.986s +2.220s 24. Vittorio Ghirelli Lazarus 1m54.435s +2.669s 25. Gianmarco Raimondo Trident 1m55.291s +3.525s 26. Mitch Evans Arden 2m00.403s +8.637s