MIL-PRF-87257B, PERFORMANCE SPECIFICATION HYDRAULIC FLUID, FIRE RESISTANT; LOW TEMPERATURE, SYNTHETIC HYDROCARBON BASE, AIRCRAFT AND MISSILE (22 APR 2004)., This specification describes the characteristics and provides the requirements for a synthetic hydrocarbon base hydraulic fluid for use in the -54°C to +200°C temperature range in aircraft and missile hydraulic systems. This hydraulic fluid is identified by NATO Code No. H-538 (see 6.5).