Racing Club, Tigre and Godoy Cruz maintained the pressure on Apertura leaders Atletico Rafaela with wins in the latest round of fixtures in Argentina.
Teofilo Gutierrez scored a 19th-minute penalty to sink visiting Olimpo and move Racing Club up to second in the table, a point behind the pacesetters.
Tigre's 3-1 win at struggling Estudiantes was based on an impressive first half performance. The visitors raced into a three-goal lead inside 24 minutes with goals from Carlos Luna, Diego Morales (penalty) and Roman Martinez, with the home side having goalkeeper Damien Albil dismissed at 1-0.
Estudiantes, second from bottom and winless after six matches, needed a 61st-minute own goal from Carlos Casteglione to get off the mark - but they were not going to stop Tigre moving up to fourth.
Godoy Cruz are up to seventh after a come-from-behind 6-1 defeat of All Boys. Eduardo Dominguez gave the visitors the lead midway through the first half but Ruben Ramirez and Emanuel Perea's own goal turned things around by half-time and Ramirez, Leandro Caruso and Diego Villar made the points safe.
Dominguez's evening took a turn for the worse on the hour when he was dismissed, with substitute Jorge Curbelo completing the scoring for the home side four minutes from time.
On Friday, Colon Santa Fe defeated San Lorenzo 3-1. Esteban Fuertes scored either side of half-time for Colon and although Emmanuel Gigliotti pulled a goal back midway through the second half, Federico made the points safe four minutes from time.
In the other match, leaders Atletico Rafaela were held to a goalless draw by mid-table Newell's Old Boys, who drew for the fourth time in six matches.