Castrol Aero™ 40 is a high quality, mineral based MIL-H-5606 hydraulic fluid containing a highly shear stable viscosity index improver, an anti-oxidant, anti-wear agents, and an approved EP additive which reduce martensitic streaking of landing gear outer cylinders and galling of shock strut upper bearings. Aero 40 is available in either dyed red (Douglas Aircraft) or undyed, straw colored (Boeing Spec BMS 3-32, Type II).