How often should brake fluid be changed?

Every 2 years regardless of mileage. Brake fluid is hygroscopic — it absorbs water from the air, lowering its boiling point and risking brake fade.

Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.

Can I check brake fluid moisture myself? — Yes — moisture test strips are about £8 from any motor factor.

Is it part of an MOT? — No, but the MOT does test brake performance — degraded fluid can cause failure.