How to Identify the Quality of Brake Fluid?
2 Answers
Substandard or poor-quality brake fluid can corrode the rubber seals in the brake master cylinder and negatively impact braking performance. To assess brake fluid quality, consider the following three key indicators: 1. Boiling Point: Inferior brake fluid has poor high-temperature resistance, easily vaporizing under heat to form visible bubbles, which create airlocks in the brake lines and hinder proper fluid flow. 2. Low-Temperature Fluidity: Based on the kinematic viscosity characteristic of brake fluid, this refers to its flowability in cold conditions. In frigid northern regions, qualified brake fluid maintains normal flow, while substandard fluid may partially or fully solidify, severely compromising braking performance. Worse, if frozen fluid expands and ruptures brake lines, catastrophic consequences may follow. 3. Corrosiveness: Methanol-based or adulterated brake fluids exhibit strong metal corrosion. Testing involves immersing metal objects to observe rust formation.
With over twenty years of driving experience, I rely on daily observations to assess brake fluid quality. First, check the color: fresh fluid is clear like water, while old fluid appears dark or cloudy, possibly indicating water contamination. Smell is another indicator—good fluid is nearly odorless, but degraded fluid emits a sharp, acidic odor. Boiling point is critical; DOT3 fluid with a wet boiling point below 160°C is unsafe, whereas DOT4 or 5.1 offers better reliability. A simple moisture test using a pen-style tester can reveal water content—replace if it exceeds 3%. Regular replacement every two years ensures long brake system life and guaranteed safety.
