Not at least because of the increased environmental awareness of many consumers, environmentally friendly hydraulic fl uids are often used in Germany like areas such as forestry or in mariti me applicati ons. According to EN ISO 6743-4 and DIN ISO 15380, hydraulic fluids of the classes HETG (nati ve esters), HEES (syntheti c esters), HEPR (mostly polyalphaolefi ns) and HEPG (polyglycols) are considered to be environmentally compatible /ISO03, OEC92, DIN01/. Against the background of the expensive raw materials and the potential competition with foodstuffs, the search for raw materials alternati ves has been intensified in recent years. IFAS is currently investigating so called Biopolymers.They have strong thickening properties when dissolved in water. Similar to polymer thickeners for mineral oil-based hydraulic fl uids (HVLP), their technical suitability depends greatly on the stability with regard to shear stresses. Against the background, IFAS was set up a fluid aging test bench which exposes the fluid to near-application shear loads as far as possible. The test rig creates a pressure of 160 bar, at 10 l/min with a pressure-relief valve /Bus95/. For the experiments with water-based media, the fl uid temperature is adjusted, for example, to 30 °C, in order to avoid cavitation effects. The presentation shows the development of the hydraulic test rig and first measurement results. They show a stability of a solution under hydraulic loads.