Is it acceptable to reuse brake fluid from another system?

Using brake fluid from another system is not considered safe due to potential contamination and degradation issues. Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. When fluid has been used in another braking system, it may contain contaminants such as dirt, metal particles, or moisture that could compromise the performance and safety of the brake system receiving the reused fluid.

Additionally, different systems might use different types of brake fluid (e.g., DOT 3, DOT 4, DOT 5), and even if they are the same type, the fluid's condition and purity are critical to effective braking performance. Reusing fluid can introduce variables that compromise the brake system's reliability and effectiveness, which is why it is always advisable to use new, clean brake fluid that meets the vehicle manufacturer’s specifications.