The Spaniard emerged from a difficult first day on the slippery gravel roads around Concepción with the advantage, completing Friday’s six stages in 49min 37.2sec.
Rosselot sits second after an impressive home showing, while Junior WRC title contender Ali Türkkan is third, 29.4sec from Membrado and just 14.3sec behind the Chilean.
That leaves the leading trio - all also competing in Junior WRC - separated by less than half a minute heading into Saturday.
Ignacio Gardiol holds fourth, 1min 52.7sec off the WRC3 lead, with Felipe Padilla fifth and Patricio Muñoz sixth.
For Membrado, the position is particularly valuable as he continues his push in both the Junior WRC and WRC3 title fights.
Saturday is the longest day of Rally Chile, with 139.2 competitive kilometres across two passes of Pelún, Lota and María las Cruces.