To obtain a foam control composition useful for controlling foams formed in a process for treating crude oil by dispersing an organosiloxane having a specified molecular weight and a specified polydispersity in a liquid organic diluent.

This composition is prepared by dispersing in a liquid organic diluent at least 0.1 wt.% organosiloxane having a weight-average molecular weight of at least 1,800,000 and a polydispersity of at most 4. Desirably, the organosiloxane is used in a concentration of 0.1-50 wt.% based on the composition. It is desirable that the viscosity of the composition is 50-5,000 mPa.s. The liquid organic diluent is exemplified by an alkane such as butane or pentane, an alkane halide such as methyl chloride, an ether such as ethyl ether, a ketone such as methyl ethyl ketone, an aromatic hydrocarbon such as toluene, or a mineral spirit, and is most desirably white spirit.