MIL-H-5606 hydraulic fluid is the recommended fluid for all Malabar jacks. Other compatible hydraulic fluids are: SAE5W, SAE10W and ATF (automatic transmission fluid). For temperatures below 32 degrees Fahrenheit, we only recommend the use of MIL-H-5606. When temperatures fall below zero degrees Fahrenheit, we recommend using MIL-H-5606 cut to 50 percent with aliphatic naphtha.