When oil is used as the main fluid and 40-percent water is added (emulsified) into the oil, it is described as a water-in-oil emulsion. These types of fire-resistant hydraulic fluids are often referred to as invert emulsions, which is to say, tiny droplets of water are suspended in the oil. This type of fluid will have better lubricating abilities than a fluid that is 95-percent water and 5-percent mineral oil with additives, but will not be as fire resistant.
