Estonian Tanak increased his overnight lead from four seconds to almost 50sec over Hyundai's Teemu Suninen.
Elfyn Evans, aiming to maintain his slender title hopes, is placed fourth, 1min 16.8sec off the pace.
Almost half a minute behind the Welshman came his Toyota teammate Kalle Rovanpera, who leads Evans by 33 points in the championship race.
With only two rounds of the season to come after Chile Evans is desperate for a decent result to prolong his battle for the WRC crown with the defending champion.
Rovanpera won the day's first stage but the Finn was then forced to nurse his Toyota's soft tyres and his hopes of wrapping up the season with two legs to spare look slim.
The final two rounds of the year are the Central European Rally, a new addition to the calendar, in Austria, Czech Republic and Germany, in late October with Japan hosting the 13th and final leg in November.
