FMVSS 116: Motor vehicle brake fluids explained.

What FMVSS 116 says it is for

The eCFR heads this section "Standard No. 116; Motor vehicle brake fluids." Under 49 CFR part 571, the Federal Motor Vehicle Safety Standards are the numbered standards that set safety performance requirements for motor vehicles and equipment. The text below is quoted from 571.116 as current through October 29, 2026.

This standard specifies requirements for fluids for use in hydraulic brake systems of motor vehicles, containers for these fluids, and labeling of the containers.

The purpose of this standard is to reduce failures in the hydraulic braking systems of motor vehicles which may occur because of the manufacture or use of improper or contaminated fluid.

What it applies to

The application section of the standard says:

This standard applies to all fluid for use in hydraulic brake systems of motor vehicles. In addition, S5.3 applies to passenger cars, multipurpose passenger vehicles, trucks, buses, trailers, and motorcycles.

Applicability is decided by the text of the standard as written, including any exclusions it lists, and by the date-specific rules in it. This page does not decide whether a particular vehicle or item is covered.

How the standard is organized

The eCFR text of 571.116 has these top-level sections:

• S1: Scope
• S2: Purpose
• S3: Application
• S4: Definitions
• S5: Requirements
• S6: Test procedures
• S7: Auxiliary test methods and reagent standards

In all, the text has 116 numbered headings. Use the finder above to search them; for example, a search for "test" lists the headings that mention tests.

Key requirements, quoted from the text

These are excerpts from the requirements sections of 571.116, in the order the standard presents them. Long paragraphs are shortened where marked; the eCFR has the complete text, tables and figures, which this page omits.

S5 Requirements. This section specifies performance requirements for DOT 3, DOT 4 and DOT 5 brake fluids; requirements for brake fluid certification; and requirements for container sealing, labeling and color coding for brake fluids and hydraulic system mineral oils. Where a range of tolerances is specified, the brake fluid shall meet the requirements at all points within the range.

S5.1 Brake fluid. When tested in accordance with S6, brake fluids shall meet the following requirements:

S5.2.1 Container sealing. Each brake fluid or hydraulic system mineral oil container with a capacity of 177 mL or more shall be provided with a resealable closure that has an inner seal impervious to the packaged brake fluid. The container closure shall include a tamper-proof feature that will either be destroyed or substantially altered when the container closure is initially opened.

S5.3 Motor vehicle requirement. Each passenger car, multipurpose passenger vehicle, truck, bus, trailer, and motorcycle that has a hydraulic brake system shall be equipped with fluid that has been manufactured and packaged in conformity with the requirements of this standard.

S6.1 Equilibrium reflux boiling point. Determine the ERBP of a brake fluid by running duplicate samples according to the following procedure and averaging the results.

S6.2 Wet ERBP. Determine the wet ERBP of a brake fluid by running duplicate samples according to the following procedure.

S6.3 Kinematic viscosities. Determine the kinematic viscosity of a brake fluid in mm 2/s by the following procedure. Run duplicate samples at each of the specified temperatures, making two timed runs on each sample.

S6.4 pH value. Determine the pH value of a brake fluid by running one sample according to the following procedure.

S6.5 Fluid stability. Evaluate the heat and chemical stability of a brake fluid by the following procedure, running duplicate samples for each test and averaging the results.

S6.6 Corrosion. Evaluate the corrosiveness of a brake fluid by running duplicate samples according to the following procedure.

S6.7 Fluidity and appearance at low temperatures. Determine the fluidity and appearance of a sample of brake fluid at each of two selected temperatures by the following procedure.

S6.9 Water tolerance. Evaluate the water tolerance characteristics of a brake fluid by running one test specimen according to the following procedure.

S6.10 Compatibility. The compatibility of a brake fluid with other brake fluids shall be evaluated by running one test sample according to the following procedure.

S6.11 Resistance to oxidation. The stability of a brake fluid under oxidative conditions shall be evaluated by running duplicate samples according to the following procedure.

S6.12 Effect on SBR cups. The effects of a brake fluid in swelling, softening, and otherwise affecting standard SBR WC cups shall be evaluated by the following procedure.

S6.13 Stroking properties. Evaluate the lubricating properties, component compatibility, resistance to leakage, and related qualities of a brake fluid by running one sample according to the following procedures.

S6.14 Container information. Each container with information marked directly on the container surface or on a label (labels) affixed to the container pursuant to S5.2.2.2 or S5.2.2.3 is subjected to the following procedure: (a) If the container has a label affixed to it, make a single vertical cut all the way through the label with the container in the vertical position. (b) Immerse the container in the same brake fluid or hydraulic system mineral oil contained therein for 15 minutes at room temperature (23 ±5 °C; 73.4 ±9 °F). (c) Within 5 minutes after removing the container from the fluid or oil, remove excess liquid from the surface of the container by wiping with a clean dry cloth.

S7.1 Distilled water. Nonreferee reagent water as specified in ASTM D1193-70 (incorporated by reference, see § 571.5) or water of equal purity.

S7.2 Water content of motor vehicle brake fluids. Use analytical methods based on ASTM D1123-59 (incorporated by reference, see § 571.5) for determining the water content of brake fluids, or other methods of analysis yielding comparable results. To be acceptable for use, such other method must measure the weight of water added to samples of the SAE RM-66-04 (see Appendix A of SAE Standard J1703 NOV83 (incorporated by reference in § 571.5)) and TEGME Compatibility Fluids (see Appendix B of SAE Standard J1703 JAN95 (incorporated by reference in § 571.5)) within ±15 percent of the water added for additions up to 0.8 percent by weight, and within ±5 percent of the water added for additions greater than 0.8 percent by weight. [excerpt continues in the eCFR]

S7.3 Ethanol. 95 percent (190 proof) ethyl alcohol, USP or ACS, or Formula 3-A Specially Denatured Alcohol of the same concentration (as specified at 27 CFR 21.35). For pretest washings of equipment, use approximately 90 percent ethyl alcohol, obtained by adding 5 parts of distilled water to 95 parts of ethanol.

S7.4 Measuring the hardness of SBR brake cups. Hardness measurements on SBR wheel cylinder cups and master cylinder primary cups shall be made by using the following apparatus and the following procedure.

S7.5 Sediment by centrifuging. The amount of sediment in the test fluid shall be determined by the following procedure.

S7.6 Standard styrene-butadiene rubber. (SBR) brake cups. SBR brake cups for testing motor vehicle brake fluids shall be manufactured using the following formulation:

S7.7 Isopropanol. ACS or reagent grade.

Defined terms

The standard defines 10 terms in its definitions section. Definitions are quoted from the eCFR.

• Blister means a cavity or sac on the surface of a brake cup.
• Brake fluid means a liquid designed for use in a motor vehicle hydraulic brake system in which it will contact elastomeric components made of styrene and butadiene rubber (SBR), ethylene and propylene rubber (EPR), polychloroprene (CR) brake hose inner tube stock or natural rubber (NR).
• Chipping means a condition in which small pieces are missing from the outer surface of a brake cup.
• Duplicate samples means two samples of brake fluid taken from a single packaged lot and tested simultaneously.
• Hydraulic system mineral oil means a mineral-oil-based fluid designed for use in motor vehicle hydraulic brake systems in which the fluid is not in contact with components made of SBR, EPR or NR.
• Packager means any person who fills containers with brake fluid that are subsequently distributed for retail sale.
• Packaged lot is that quantity of brake fluid shipped by the manufacturer to the packager in a single container, or that quantity of brake fluid manufactured by a single plant run of 24 hours or less, through the same processing equipment and with no change in ingredients.
• Scuffing means a visible erosion of a portion of the outer surface of a brake cup.
• Sloughing means degradation of a brake cup as evidenced by the presence of carbon black loosely held on the brake cup surface, such that a visible black streak is produced when the cup, with a 500 ±10 gram deadweight on it, is drawn base down over a sheet of white bond paper placed on a firm flat surface.
• Stickiness means a condition on the surface of a brake cup such that fibers will be pulled from a wad of U.S.P. absorbent cotton when it is drawn across the surface.

Limits of this page

This page quotes the text of 49 CFR 571.116 as published in the eCFR, current through October 29, 2026. It omits tables, figures, cross-referenced test procedures in other parts, and the preambles and rulemaking history that explain the rule. It does not tell you whether a given vehicle, part or product complies, how to run a test, or what a manufacturer must certify. Compliance questions go to the manufacturer's engineers, qualified counsel or NHTSA. The eCFR is an editorial compilation, not the official legal edition of the Federal Register.

Sources

Sources opened and read November 2, 2026.

• eCFR: 49 CFR 571.116, Standard No. 116; Motor vehicle brake fluids. (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR part 571, Federal Motor Vehicle Safety Standards (current through October 29, 2026) (read November 2, 2026)