DOT 3 brake fluid is a type of fluid designed for hydraulic brake systems and is based on glycol. The key parameter is the boiling point. For the new, so-called 'dry' fluid, a minimum boiling point of 205 °C is specified. As the fluid is hygroscopic, meaning that it absorbs moisture in the air, its boiling point decreases over time. For a 'wet' liquid with a water content of around 3,7 %, the boiling point must not fall below 140 °C. If the boiling point is exceeded, for example during heavy braking, compressible vapour bubbles would form in the fluid, causing the brake pedal to sink and reducing braking performance.