Tribological Performance of Glycerol-Based Hydraulic Fluid Under Low-Temperature Conditions

This study evaluated the tribological performance of a glycerol-based hydraulic fluid as a green alternative to conventional mineral-based hydraulic lubricants under low-temperature conditions, down to −20 °C. The performance of the glycerol hydraulic fluid (GHF) was compared against that of a mineral hydraulic fluid (MHF) using an SRV tribometer for steel-to-steel sliding contact under boundary lubrication conditions. Comparisons were also made at a moderate temperature to assess the fluids’ performance across different thermal conditions. The results show that the GHF demonstrated up to 55% lower friction coefficients under various test conditions than the MHF. With wear volumes up to 90% lower, the GHF produced thinner and less intense wear scars on the test discs compared to the deeper and more pronounced scars observed with the MHF. We conducted rheological tests which also revealed the green fluid’s stable viscosity transition with temperature changes and its Newtonian behaviour under the measured shear conditions, which may indicate its ability to maintain consistent lubrication.