Then you have a leaking brake line, brake caliper, or leaking wheel cylinder. Just start looking from the brake lines from the master cylinder on down to each wheel, you should be able to see a wet area from where it is leaking.
It's B R A K E fluid and it has a leak. Listen to Rowefast!
It should not use ANY brake fluid. Any loss of fluid is unacceptable and a major safety hazard.
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