Olimpo's plight at the foot of Argentina's Clausura continues after a 2-0 defeat to Union Santa Fe.
Jorge Velazquez and Matias Donnet netted inside the last 18 minutes as the home side moved up to seventh and inflicted a sixth defeat in seven away games on the bottom club.
Arsenal Sarandi missed out on the chance to join second placed Newell's Old Boys on 22 points as they slipped to a 2-0 defeat at San Lorenzo.
Juan Salgueiro opened the scoring in the 31st minute and Emmanuel Gigliotti doubled the lead 11 minutes from time as San Lorenzo moved into the top half.
In the other match played, Argentinos Juniors are still seeking a first home win after a goalless draw with Atletico Rafaela.