Brakes convert kinetic energy into heat. Part of this heat is absorbed by the brake fluid. If the brake fluid begins to boil, so-called vapour locks will be created. This results in brake failure. For this reason the brake fluid must have a high boiling point (dry boiling point). However, glycol based brake fluid absorbs moisturefrom the air (hygroscopic), which in the long term lowers the boiling point and reduces performance. After 2-3 years, depending on the specification and quality of the brake fluid, the boiling point can drop down to under 170 °C.