The brake fluid covered by this specification is military unique due to the more stringent requirements in the areas of boiling point (both wet and dry), low temperature viscosity, and corrosion protection. It is intended for use as an operational fluid and preservative fluid in automotive fully hydraulic (i.e. not actuated by air) anti-lock brake systems (ABS) at ambient temperatures ranging from -55 °C to 55 °C; the brake fluid itself is only operational down to fluid temperatures of -40 °C. While compatible, this fluid is not intended to be used in military ground equipment without ABS, or in systems that utilize an air-over-hydraulic ABS where the brake fluid is not used to actuate the ABS. In these cases, the standard military silicone brake fluid under MIL-PRF-46176 should be used. Table II lists the National Stock Numbers (NSN) that have been established for MIL-PRF-XXXXX.

As a general recommendation, the drain interval on PBF is two years. At this time, use of PBF should be approved by a Lubrication Order, Technical Manual, Maintenance Action/Information Message, or by a representative of the equipment's Product Manager (PM) or other designated representative (e.g., equipment specialist/LAR).

Replacement of brake fluid.

If brake fluid in accordance with this specification is used to replace another type of polyglycol brake fluid (e.g. DOT 3, DOT 4), adequate flushing of the brake system must be accomplished to remove all traces of the brake fluid that is to be replaced. If these fluids are not completely removed, the viscosity properties and high boiling point protection can be somewhat diminished. If changing from a silicone brake fluid (e.g. DOT 5, MIL-PRF-46176), contact U.S. Army DEVCOM GVSC for guidance and instructions; silicone brake fluids have a different base chemistry and are not miscible with water unlike polyglycol brake fluids. This incompatibility will cause phase separation and possible damage to the brake system if not properly flushed.