Abstract: The invention relates to a method for treating and conditioning circulated rolling oil, comprising removing dirt and abrasion particles from the returned rolling oil by filtration, feeding filter aids in a controlled manner, and adjusting an electric conductivity preventing electrostatic charging in the purified rolling oil. So that conductivity additives can be omitted, a flocculating agent is employed as the filter aid, and the amounts in which the agent is added depends on the residual contamination remaining in the filtrate, so that a preset minimum conductivity caused by the remaining residual contamination is preserved in the filtrate.