What is the Difference Between Good and Bad Brake Fluid?
3 Answers
Brake fluid quality is distinguished based on its grade. The following are the differences between good and bad brake fluid: 1. High-temperature performance: Poor-quality brake fluid has inferior high-temperature resistance and is prone to vaporization under high temperatures, forming easily observable bubbles. This creates air resistance in the brake system pipelines, hindering the proper flow of brake fluid. 2. Corrosion to metal objects: Brake fluid mixed with methanol or blended alcohols and water can be highly corrosive to metal objects. Placing a metal object in the fluid and observing whether it rusts can help identify its quality. 3. Kinematic viscosity: Brake fluid has the characteristic of kinematic viscosity, which refers to its flowability at low temperatures. In extremely cold northern regions, qualified brake fluid can still flow normally, while inferior brake fluid may exhibit varying degrees of solidification. In this state, the brake fluid essentially loses its braking performance. Moreover, if the brake fluid freezes and expands, it can rupture the brake lines, leading to even more severe consequences.
As a driver who frequently travels long distances on highways, I have personally experienced the difference between good and bad brake fluid. High-quality brake fluid has a high boiling point, preventing vaporization during emergency braking and maintaining responsive and powerful braking. Inferior fluid has a low boiling point and strong water absorption, leading to longer braking distances or even failure due to accumulated moisture. I once used cheap fluid and felt the pedal go soft during continuous downhill driving. Later inspection revealed the fluid had deteriorated and corroded the calipers. I recommend choosing DOT4 or higher-grade products, which are more heat-resistant, moisture-resistant, and compatible with ABS systems. Changing it every two years can prevent these issues and ensure driving safety—don’t gamble with your life.
In the car enthusiast community, discussions about brake fluid often focus on its composition details. High-quality fluids use premium glycol-based or silicone-based formulations, which are less prone to moisture absorption and maintain stable boiling points, ensuring smooth flow at low temperatures. Inferior fluids may contain more impurities, easily absorb moisture from the air, experience rapid boiling point degradation, and cause corrosion in the hydraulic system along with bubble retention. From some tests I've seen, DOT 5.1 fluid performs better in humid environments, while poor-quality fluids can lead to abnormal brake pedal rebound. Pay attention to color changes during replacement—light yellow indicates freshness, while darkening or cloudiness means it's time for a change. Never delay until the pump fails and requires repair.
