GB 12981-2025Motor vehicle brake fluids (English PDF)

1 Scope

China's mandatory national standard for motor vehicle brake fluids. Brake fluid is the only component of a car whose failure removes the brakes entirely and without warning, and the mechanism is specific: the fluid is hygroscopic, absorbing water from the atmosphere through the hoses and the reservoir over years, and water lowers the boiling point. On a long descent the fluid at the calliper reaches that lowered boiling point, vapour forms, and vapour is compressible - so the pedal goes to the floor exactly when the brakes are needed most. That is why the standard specifies two boiling points, dry and wet, the wet one measured after the fluid has been humidified to represent a fluid that has been in service. Around them sit the viscosity at low temperature, which governs ABS response in the cold, and the compatibility with the rubber of the seals.

This document specifies the product types and labeling, technical requirements and test methods, inspection rules and marks, packaging, transportation and storage of non- petroleum-based brake fluids used in hydraulic braking and clutch systems of motor vehicles. This document applies to motor vehicle brake fluids that come into contact with seals made primarily of styrene-butadiene rubber (SBR) or ethylene propylene diene monomer (EPDM), and are based on non-petroleum-based raw materials (alcohols, alcohol ethers, and their compounds) with the addition of various additives.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 265, Petroleum Products -- Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity

GB/T 514, Specification for liquid-in-glass thermometers for testing of petroleum products

GB/T 531.1, Rubber vulcanized or thermoplastic -- Determination of indentation hardness -- Part

3 Terms and definitions

This document does not contain any terms or definitions that need to be defined.

4 Product types and labeling

4.1 Product types This document pertains to a series of non-petroleum-based brake fluids for motor vehicle hydraulic braking and clutch systems. The product series is named HZY, where H, Z, and Y are the first letters of the first Chinese characters in the Chinese words for "synthetic", "braking" and "liquid" respectively. Based on different operating temperature and viscosity requirements, the products are divided into five grades. HZY3, HZY4, HZY5, HZY6, and HZY7, corresponding to Class 3, Class 4, Class 5.1, Class 6, and Class 7 in ISO 4925.2020, respectively. HZY3, HZY4, and HZY5 correspond to DOT3, DOT4, and DOT

5.1 brake fluid types from the U.S. Department of Transportation.

4.2 Product labeling Brake fluid products shall be labeled with at least the following. product grade, motor