The BMW Team Germany man clocked the fastest lap of 1:25.463 a little after halfway, beating defending champion Yvan Muller by 34 thousandths.
Andy Priaulx (1:25.567) and Augusto Farfus (1:25.610) were third and fourth respectively but the Brazilian youngster ended the session prematurely when his car got stranded on the gravel trap at the last corner.
Alain Menu completed a lap of 1:26.033 and placed his Chevrolet Cruze in seventh position but team-mate Robert Huff spun at the Esse da Baixa in the dying minutes.
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Felix Porteiro continued to impress and posted the ninth fastest lap, dominating the Independents' field.
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