Yvan Muller posted the fastest lap of 1:24.808 halfway through the session, ousting his team-mate Rickard Rydell, who had led since the early minutes.
Rydell clocked 1:24.992 on his first lap out of the pits and later improved to 1:24.835.
The Swede was placed second behind Muller, with the other SEAT Sport men behind.
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Tiago Monteiro went around in 1:24.963, Jordi Gene managed 1:25.037 – the first provisional fastest lap of the session - and Gabriele Tarquini 1:25.042.
Local boy Augusto Farfus and his BMW emerged as the best of the rest, setting the sixth-fastest lap of 1:25.069.
As in testing on Friday, Felix Porteiro, ninth overall with a time of 1:25.510, and Nicola Larini, 10th in 1:25.572, were the fastest of the Independents and Chevrolet team respectively.
Jaap van Lagen led the LADA trio with a lap of 1:26.936 that placed him in 20th position.
The session was red-flagged with six minutes remaining when Kirill Ladygin's LADA crashed into the barrier at the last corner.
Just before the end of the session, Alessandro Zanardi went off at the same corner, beaching his BMW in the gravel trap.
Andy Priaulx completed only two laps due to a brake failure.
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