General Information about Brake Fluid

Brake fluid is hydroscopic (absorbs water). When fresh from the can, it can be considered "dry" with the higher boiling point. That's why racers and people doing driver's schools change the brake fluid just before events. Over time, brake fluid absorbs water lowering its boiling point to the "wet" level.

Brake fluids improperly packaged in a plastic bottle can take on moisture while still on the store shelf.

For street cars, wet boiling point numbers are more important than dry because the fluid stays in your car for quite a while (one to two years). After a few months, with exposure to humid air, the brake fluid performance is probably closer to the wet than dry point.

Brake fluid is one of the most overlooked aspects of brake system maintenance - but needs to be changed more frequently than most people think for two reasons, maintenance and performance. It generally takes about a quart to flush the system.

Changing old brake fluid removes water from the brake system. Brake fluid is hydroscopic, it absorbs water. Old brake fluid must be flushed out or water absorbed by the fluid eventually causes internal rust on the disk calipers and pistons.

Changing old brake fluid helps high temperature operation because fresh (dry) brake fluid has a higher boiling point than older (wet) brake fluid. If brake fluid boils, compressible gas bubbles form, resulting in a very spongy brake pedal.

Normal or Fleet Applications - Use a high quality fluid such as Z-Rated® that comes in a metal container and meets DOT requirements. Change with every brake job or every six months to one year - whichever comes first - to provide the maximimum stopping power and avoid that mushy pedal feel. Competition (motorsport) Applications - Change your Z-Rated® before every race.