Because your car's brake system is so vitally important, it is essential that use high quality brake fluid in your vehicle to help avoid mishaps in the braking system. Brake fluid is used to transfer the force and pressure created in hydraulic lines to the mechanical brake system on the wheels of your car. Brake fluid does run low occasionally and will need to be topped off. When you fill your car's brake fluid reservoir, you will want to make sure you use a good quality fluid.
Best Types of Brake Fluid
Brake fluid is rated on its ability to withstand high boiling points. Brake fluids with rather low boiling points seem to dissipate and evaporate faster, and may result in a loss of pressure needed for proper braking. The United States Department of Transportation (DOT) requires minimum boiling point levels for brake fluid sold in the U.S.
Most types of brake fluid are hygroscopic, meaning that they will absorb water from the air; therefore, brake fluid is rated by its boiling point when it is dry (before water absorption) and when it is wet (after water absorption). DOT 3 brake oil meets the U.S DOT minimum boiling point levels of 401 degrees when dry and 284 degrees when wet. While this is considered satisfactory, many people choose DOT 4 brake fluid which has higher boiling points of 446 and 311 degrees respectively. DOT 5 brake fluids are available, but are not generally recommended because they don't offer much more protection than do DOT 4 level brake fluids and are more expensive.
Most brands of DOT 4 brake fluids will perform well for normal driving. However, if you make frequent hard and quick stops, you might want to consider brands like Castrol, Ford Heavy Duty and Motul as theses brands all tend to have boiling point ratings much higher than DOT minimums and provide excellent pressure transfer.