Teenager Kalle Rovanperä led the WRC 2 class by 23.2secs after six consecutive stage wins overturned his Skoda Motorsport team-mate’s Friday advantage.
Pontus Tidemand came into Saturday with a 20.2sec lead in his Fabia R5 but the 17-year-old Finn was flying from the off - taking 4.5sec out of the Swede on the opening SS9 test.
However, it was in the fog where Rovanperä really shone. On the 40.48km Cuchilla Nevada/Rio Pintos test, he finished almost 30sec ahead of Tidemand thanks to his fearlessness through fog that reduced visibility to 20 metres in the opening kilometres.
From then on, he was the picture of calm as he edged the head-to-head SS12 by 0.3sec to round out the morning loop. He also won SS13 and SS14, but a desire to avoid a puncture and preserve his lead allowed Tidemand to claim a win on the second run of the 40.48km mammoth stage.
The Fabia R5 driver said: "We are going quite well, but we have to really push because Pontus is doing well. I just played it safe, I didn't want to get a puncture. It's going to be interesting tomorrow."
Third place went to Gus Greensmith, who is more than two minutes behind the Skoda pair after a clean run through the seven stages in his Fiesta.
Pedro Heller is fourth, with Diego Dominguez in fifth after he was given a 50sec time penalty for leaving service late.
Sixth place is held by Gustavo Saba who rejoined this morning after a mechanical issue last night.
Marquito Bulacia, who held sixth place on Friday night, retired after crashing his Fiesta in SS9.
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