With one leg remaining, the Estonian led Sébastien Ogier by 30.3sec. A charging Sébastien Loeb rolled back the years to close to within 5.1sec of fellow Frenchman Ogier after a stirring drive on the fast gravel tracks.
Series leader Thierry Neuville suffered a huge blow after a violent crash in his Hyundai i20. His car was destroyed when it rolled seven times after drifting wide in a fast corner, but the Belgian and co-driver Nicolas Gilsoul escaped with bruising. Neuville had been third.
Tänak won two of the six speed tests, covering 121.16km, in his Toyota Yaris, keeping Ogier at arm’s length all day.
“It was a tough day and in these kind of conditions it’s difficult to control anything. I tried to find a good rhythm but in the last stage, with fog, rain and the wrong tyres, everything was wrong. We made it through and the gap is good, but we need to focus tomorrow,” he said.
Ogier wanted more pace from his Citroën C3 during the morning. He gambled with tyre choice this afternoon and was happier with his speed, although the bad weather in the final stage allowed nine-time world champion Loeb to close in.
Loeb, driving an i20 on gravel for the first time, was the quickest driver today. He won two stages and only finished outside the top three times once as he gained in confidence to charge from an overnight sixth.
He was locked in battle with Jari-Matti Latvala but the Finn’s impressive drive came to a sad end when he hit a rock in the final test and broke his Yaris’ driveshaft. He is expected to restart tomorrow.
Elfyn Evans ended half a minute behind Loeb in fourth in his Ford Fiesta. He lacked stability in the high-speed sections but had almost two minutes in hand over young team-mate Teemu Suninen, who moved up from ninth to fifth.
Esapekka Lappi had an improved day in his C3 to claim sixth, ahead of Andreas Mikkelsen, whose confidence improved after mid-leg set-up changes to his i20.
WRC 2 Pro leader Kalle Rovanperä, Mads Østberg and Kris Meeke filled the leaderboard. Meeke’s fifth place disappeared in the opening test when he ran wide, struck a tree stump and rolled his Yaris. He dropped four minutes but battled on for the rest of the morning with no windscreen.
Sunday’s final leg is the shortest, with four stages covering 58.38km near host city Concepción. Two runs through the Bio Bió test, the second of which forms the Wolf Power Stage and offers bonus points to the fastest five drivers, sandwich two longer tests.