They may lose their lead in championship standings over the weekend and they are only one place above the bottom three, who go down, in the separate relegation table based on teams' average points over three seasons.
Argentinos are top with 13 points from seven matches, one point ahead of Lanus, Arsenal and San Lorenzo and two in front of title holders Newell's Old Boys.
Winger Lautaro Acosta put Lanus in front midway through the first half, running onto former Boca Juniors team mate Santiago Silva's neat chip to steer a low shot past goalkeeper Pablo Migliore.
Argentinos' better start to the second half was nipped in the bud in the 56th minute when Uruguayan Silva chested down a right cross to the far post from midfielder Leandro Somoza and, like Acosta, scored his fourth goal of the championship.
Somoza, the third of a trio who moved to Lanus from Boca in the off-season, hit a brilliant third 10 minutes later with a rising shot from 20 metres into the top corner.
Substitute Lucas Melano completed the rout with Argentinos conceding one more goal in the match than they had in their previous six.
Newell's are at home to Olimpo in Rosario and San Lorenzo host Godoy Cruz on Saturday, while Arsenal receive River Plate at the Julio Grondona stadium on Sunday.
The weekend's big clash is at La Bombonera on Sunday where 11th-placed Boca (nine points) host fellow big guns Racing Club, who languish at the bottom with two points.