In industries such as steel- and aluminum-processing mining and aviation, fire-resistant fluids are often an important consideration in choosing a hydraulic fluid. Water-based hydraulic fluids are often an excellent choice when fire resistance performance is the key selection criteria. However hydraulic pump reliability can sometimes be a challenge, especially when equipment is operating under high temperatures and pressures. Anhydrous hydraulic fluids are an alternative choice for more severe operating conditions. Fire-resistant phosphate esters are known to offer good fire resistance, but concerns about stability, toxicity, and cost has led to innovation in the development of other anhydrous fire-resistant products using synthetic esters, vegetable oils, and polyalkylene glycols (PAG). A comparison of the performance of non-phosphorus-based anhydrous hydraulic fluids including a synthetic ester, two conventional PAGs, and a new technology based on an oil-soluble PAG (OSP) has been undertaken. In high-temperature oxidation studies, PAGs and an OSP exhibited superior oxidation resistance compared to a synthetic oleate ester. All fluids exhibited excellent hydraulic vane pump wear performance but the ester showed high viscosity deterioration. An unusual feature of the OSP fluid was its superior air release properties. This may have practical benefits for hydraulic systems that use smaller reservoirs where cycle times are short. An examination of their fire-resistance properties using a manifold test showed the ester fluid to have higher ignition temperatures but lower ignitability factors than the PAGs and OSP fluids in the stabilized flame heat release spray method. Conventional PAGs have been used as fire-resistant fluids for over 20 years. Initial fire-resistance testing suggests that the new OSP technology has similar performance and provides performance advantages such as better low-temperature properties, faster air release, improved oxidation stability, and compatibility with hydrocarbon fluids.