ISO 4925:2026

Overview

ISO 4925:2026 is an international standard developed by the International Organization for Standardization (ISO) that specifies the requirements, specifications, and test methods for non-petroleum-based brake fluids used in hydraulic systems of road vehicles. This standard ensures that such brake fluids are compatible with hydraulic brake and clutch systems that utilize styrene-butadiene rubber (SBR) and ethylene-propylene diene monomer (EPDM) elastomer seals, such as cups and double-lipped gland seals. Adherence to ISO 4925:2026 helps manufacturers and suppliers ensure product performance, safety, and global market compatibility.

Key Topics

• Scope and Compatibility:
  ISO 4925:2026 covers non-petroleum-based brake fluids intended for hydraulic systems and specifies their compatibility with seals and components made of SBR and EPDM.

• Performance Requirements:
  The standard defines a series of performance benchmarks, including viscosity, boiling points (Equilibrium Reflux Boiling Point - ERBP), chemical stability, corrosion resistance, fluidity at low temperatures, pH, water tolerance, and effects on rubber components.

• Test Methods:
  Comprehensive testing procedures are outlined for:

  • Viscosity measurement at various temperatures
  • Boiling point assessment (wet and dry conditions)
  • Corrosion evaluation on various metals
  • Fluid stability at different temperature and humidity ranges
  • Compatibility and miscibility checks with reference fluids
  • Quantification of wear and resistance to noise in EPDM-metal contact

• Classification:
  Brake fluids are classified according to their specifications, ensuring suitability for various applications and vehicle requirements.

Applications

ISO 4925:2026 is critically important for:

• Automotive Manufacturers:
  Vehicle producers rely on these specifications to validate brake fluid formulations, ensuring long-term safety and reliability of hydraulic brake and clutch systems.

• Brake System Suppliers:
  Component and fluid manufacturers use this standard to design products and seals that maintain performance and resist degradation when exposed to approved non-petroleum-based brake fluids.

• Aftermarket Service and Maintenance:
  The standard is essential for service professionals who must select and replace brake fluids that meet global safety, compatibility, and performance criteria, reducing the risk of component failure and enhancing operational safety.

• Testing Laboratories:
  Laboratories and quality assurance teams use the standardized testing procedures to ensure product conformity and to troubleshoot field issues related to brake fluid performance.

• Regulatory Compliance:
  Compliance with ISO 4925:2026 assists manufacturers in meeting international automotive regulations and accessing global markets.

Related Standards

• ISO 4926:
  Specifies requirements for non-petroleum-based reference fluids used in testing hydraulic braking systems.
• ISO 3104:
  Outlines methods for determining the viscosity of petroleum products and lubricants, referenced for viscosity measurements in brake fluids.
• ISO 37, ISO 48-2, ISO 812, ISO 815-1, ISO 815-2:
  Detail the properties and test methods for rubbers used in seals and components.
• ASTM Standards (e.g., ASTM D 1120, ASTM D 1121):
  Provide test methods for boiling points, reserve alkalinity, and water content in brake fluids.
• DIN 51834-5:
  Specifies tribological test methods for evaluating friction-induced noise in EPDM-metal contacts.

Practical Value

ISO 4925:2026 enables the global automotive industry to standardize on high-performance non-petroleum-based brake fluids, ensuring safety, longevity, and regulatory compliance of hydraulic braking systems. The standard's rigorous requirements for chemical, thermal, and mechanical stability, combined with comprehensive test methods, support reliable operation under varied conditions and contribute to advancements in vehicle safety technology. By following ISO 4925:2026, manufacturers and users can ensure compatibility across global markets, and maintain confidence in the integrity and performance of vehicle brake fluid systems.