Gabriele Tarquini placed his SEAT at the top of the timesheets end the end of second free practice in Valencia.
The Italian veteran, who claimed pole position at Monza three weeks ago, claimed P1 in the final moments of the session, denying Chevrolet's Rob Huff by just nine thousandths of a second.
Huff again had to play second best, having narrowly lost out to teammate Yvan Muller in first practice. Muller ended FP2 in second place, within a tenth of Tarquini.
Tom Coronel had led much of the session in his BMW, but fell down to fourth by the end, losing out to Muller by just 0.003s and exactly a tenth shy of Tarquini.
Alain Menu was fifth in the third factory Cruze, just ahead of Tarquini's teammate Aleksei Dudukalo who was the leading Yokohama Trophy driver. Rival Norbert Michelisz was just behind, and only two tenths off the outright pace in seventh.
Darryl O'Young was eighth fastest as he looks to banish the mechanical demons of Monza, ahead of two more Leons; the Sunred-powered Tiago Monteiro and fellow Tuenti Racing Team driver Pepe Oriola.
Former BTCC contenders Tom Boardman, Alex MacDowall, James Nash and Tom Chilton filled positions 13 to 16 – with just a mere 0.126 separating the quartet.