Oil-based defoamers have an oil carrier. The oil might be mineral oil, vegetable oil or any other oil that is insoluble in the foaming medium, except silicone oil. An oil-based defoamer also contains a wax and/or hydrophobic silica to boost the performance. Typical waxes are ethylene bis stearamide (EBS), paraffin waxes, ester waxes and fatty alcohol waxes. These products might also have surfactants to improve emulsification and spreading in the foaming medium.
These are heavy duty defoamers and are normally best at knocking down surface foam.