Brake fluid absorbs moisture as it is hygroscopic. When this happens it lowers the boiling point which in time can cause a spongy pedal and loss of braking efficiency which will have a negative effect on your braking ability.
The water absorption is greatly increased with the combination of time and mileage.
Below it shows how the boiling point of BMW DOT 4 Brake Fluid which can be severely reduced when contaminated with water & classed as Wet compared to when new & Dry with no water content.
Dry Boiling Point
Wet Boiling Point
BMW BRAKE FLUID CHANGE - £69
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