Debutant Esteban Guerrieri was a surprise leader in World Touring Car Championship practice in Argentina, topping both sessions at Termas de Rio Hondo
Argentinian Guerrieri, who is making a one-off appearance in the championship in a second Campos Racing Chevrolet Cruze this weekend, was a surprise leader in the opening half-hour session by more than a second from the Citroen of Yvan Muller, having used a new set of tyres to set a best time of 1m43.577 seconds.
Having set the initial pace in the second session, he dropped down the order as others improved on their second runs, but vaulted back to the top of the times with his final lap - a 1m43.247s - to ensure a practice clean-sweep.
"We obviously took advantage of new tyres for me but the good thing is I feel comfortable with the car," said Guerrieri.
"We could keep a good rhythm after three laps, which is a good sign.
"I am very impressed with the team and the guys, they do everything with a lot of concentration.
"We couldn't ask for more but we're just going to be patient; it's a long day.
"We can't get too much excited for what has just happened but we will keep building up for the weekend."
Compatriot and double champion Jose Maria Lopez got closest to Guerrieri's pace, finishing the session 0.139s down in his Citroen C-Elysee ahead of team-mate Muller.
Leading Sebastien Loeb Racing driver Tom Chilton could only manage the 13th-fastest time in his independent C-Elysee in the first session, but ended the second in fourth, one tenth slower than factory driver Muller.
Tiago Monteiro was the leading Honda driver in the second session, one place ahead of team-mate Rob Huff.
Norbert Michelisz was third-fastest in the opening session, but only eighth in the second, with the ROAL and Munnich Motorsport Chevrolets of Tom Coronel and the returning James Thompson either side of the Hungarian respectively.
In his second weekend in the WTCC, Norbert Nagy brought up the rear of the field in the second session after failing to set a time in Zengo Motorsport's sole entry for the weekend.
Uruguayan Mauricio Lambiris had agreed a provisional deal to make his WTCC debut in the team's second Civic this weekend, but with Zengo opting to cut back the number of staff it brought to Argentina as a result of regular driver Ferenc Ficza's absence - the Hungarian recovering after an operation to remove his appendix - the car could not be readied in time.
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