## 1 Introduction
[PERSON] and [PERSON] presented a comparison of test results for hydrodynamic clutches filled with water and with a typical hydraulic oil, ISO VG 32 [8]. On the basis of the obtained results, it was found that the power transferred by the clutch filled with water increased by approximately 15% in relation to the clutch filled with the hydraulic oil. To prevent water leakage and decrease friction between the moving elements of the clutch, special self-lubricating sealings were applied, as well as small gaps and water additives. The newest type of working fluid used in hydraulic devices, including hydrodynamic clutches, is the two-component fluid, mainly electrorheological fluids [9; 10; 11]. The solid phase of electrorheological fluids consists of organic or inorganic particles, easily polarized by an electric field. The liquid phase consists of liquids which do not conduct electricity, such as mineral oils, plant oils, liquid paraffins and kerosene. Additives used to enhance the electrorheological effect are as follows: water, acids, inorganic salts, alcohols and esters. In order to reduce the non-ecological contents in electrorheological fluids, the solid phase consists of natural products, such as starch, cellulose, resins and rubber. A two-component electrorheological fluid that is often used is the fluid made of starch and silicon oil. Apart from their food applications, oils and vegetable fats, as well as substances obtained from them, are important raw materials used in a number of industry sectors. It is used, among other things, in cosmetics, pharmaceuticals, biofuels, paints, adhesives, coatings, surfactants, solvents and adjuvants [12; 13]. Products made using plant oils are friendly to the environment and human health, and they are biodegradable in most cases [14; 15; 16]. The use of plant oils as lubricants has a long history, dating back to olive oil usage in ancient times. Vegetable oils are useful as base materials for the production of working fluids, which results from their beneficial properties, such as a high flash point, high viscosity and low evaporation losses. The wide use of working fluids based on oils and vegetable fats is limited by their low oxidative and hydrolytic stability, low durability and high viscosity when exposed to low temperatures. These disadvantages can be successfully reduced by using appropriate chemical additives or proper preparation technology [17]. The use of plant oils in technology on a large scale faces another obstacle, which is ethical principles, namely objecting to the use of food-based raw materials for non-nutritional purposes when some parts of the world suffer from hunger. Due to that, there is an ongoing search for new raw materials, allowing for the withdraw from using oil plants used mainly for food purposes. The newest research concerns inedible oils as well as agri-food industry waste. A significant obstacle in using this waste is that it is low in oil (usually below 20% of its weight). This means that obtaining oils from agri-food waste is expensive when using classic methods, such as cold pressing or extraction with fatty solvents. Employing modern extraction methods, including supercritical fluid extraction, allows for the economically justified production of oils from raw materials low in fatty compounds. Supercritical fluid extraction is currently a technologically advanced method of separating substances from plants, used, for example, to extract caffeine from coffee, hop resins from hop cones and oils from oily raw materials. The basis of this process is the use of carbon dioxide in a supercritical state, whose properties are a density close to that of a liquid, a viscosity similar to a gas's viscosity, and a diffusion coefficient that is an intermediate between liquids and gases. Due to these properties, it has a high ability to dissolve and extract oils.