What should you avoid doing with brake fluid?

Avoiding mixing brake fluid with other fluids is critical because different types of brake fluid have varying chemical compositions. For instance, the most common types are DOT 3, DOT 4, and DOT 5, each with different properties, including boiling points and chemical makeup. Mixing these fluids can lead to issues such as reduced effectiveness, corrosion of brake components, and even brake failure. This is particularly important as brake fluid is hygroscopic, meaning it absorbs moisture from the air, which can affect its performance.

While heating brake fluid and using it beyond its expiration can certainly compromise its performance, the act of mixing it introduces immediate risks of incompatibility that can lead to system failures. Applying brake fluid directly to brakes is also problematic, as it can damage the brake components and adversely affect braking performance, but it does not have the immediate chemical conflict that mixing does. Therefore, the primary concern in ensuring brake system integrity is to never mix different types of brake fluid.