AMSOIL Series 500 High-Performance DOT 3
& AMSOIL Series 600 Racing DOT 4 Brake Fluids

What is Brake Fluid?

Brake fluid is a type of hydraulic fluid. It is used to transfer force under pressure from where it is created through hydraulic lines to the braking mechanism near the wheels. Braking applications produce a lot of heat, so brake fluid must have a high boiling point to remain effective and must also not freeze under normal temperatures.

Cause of Brake Fluid Failure

Brake fluids fail either because they boil or because they cease to provide adequate lubrication and corrosion protection. Both reasons for failure are the result of contamination, usually by water or petroleum products.
     DOT 3 and DOT 4 glycol brake fluids are hygroscopic, which means they absorb water easily and hold it in suspension, much like antifreeze. As soon as the cap is removed from a bottle of brake fluid, the brake fluid begins absorbing water from the air. And while brake fluid is kept in a closed system, moisture seeps into the brake system continuously through the various seals and microscopic pores of the flexible brake lines. This seepage can accelerate as a vehicle ages and there's no limit to how much water brake fluid can absorb.
     Water lowers the boiling point of brake fluid, which will eventually lead to failure. After two years of service, the average boiling point of brake fluid will have dropped below the minimum federal requirements.

Boiling Points Determine Protection and Reliability

As the brake system heats up, brake fluids with low boiling points begin to vaporize. The brake pedal must travel further to apply the same amount of force on the brakes, causing a spongy feeling. If enough of the brake fluid vaporizes, brake system failure may occur. Brake fluid boiling points are measured on two separate equilibrium reflux boiling point (ERBP) scales:

• Dry ERBP - the boiling point of new, freshly-opened, unused fluid

• Wet ERBP - the boiling point of a brake fluid after it has absorbed three percent water

The Department of Transportation (DOT) has set minimum standard requirements to ensure brake fluids will provide adequate protection. (Note: Because brake fluids are hygroscopic, the wet boiling point is of much greater concern than the dry boiling point.)

Minimum Standard Requirements for DOT 3 Brake Fluid:

• The minimum dry ERBP for DOT 3 brake fluid is no less than 205°C (401°F)

• The minimum wet ERBP is 140°C (284°F)
  Note: It only takes four percent water contamination to bring a DOT 3 fluid’s boiling point down to the federal limit.

Minimum Standard Requirements for DOT 4 Brake Fluid:

• The minimum dry ERBP for DOT 4 brake fluid is 230°C (446°F)

• The minimum wet ERBP is 155°C (311°F)
  Note: Their higher boiling points make DOT 4 fluids appropriate for high-performance cars and motorcycles and for vehicles used for towing.
   

Water Contamination Lowers the Boiling Point of Brake Fluid

After two years of service, the average boiling point of brake fluid will have dropped below the minimum federal requirements

AMSOIL Break Fluids Exceed Government Standards

AMSOIL Break Fluids far exceed the minimum standard requirements set by the DOT. AMSOIL Brake Fluids feature high wet boiling points for maximum life, superior performance and reliable braking, even in extreme conditions. AMSOIL Brake Fluids maintain a stable viscosity over a wide temperature range and flow easily at the highest pressures generated in automotive brake systems. They keep water in suspension, slowing its effects on the brake system.

AMSOIL Series 500 High-Performance DOT 3 Brake Fluid

• Dry ERBP of 274°C (525°F)

• Wet ERBP of 156°C (313°F)

AMSOIL Series 600 Racing DOT 4 Brake Fluid

• Dry ERBP of 304°C (580°F)

• Wet ERBP of 210°C (410°F)

Superior Additive Package

AMSOIL Brake Fluids are formulated with the best zinc-based anti-corrosion additives and pH stabilizers. They are designed for high-temperature stability, yet flow easily at low temperatures. AMSOIL Brake Fluid's superior additive package provides good lubrication throughout the system.

Compressibility

When a fluid is non-compressible it means it won’t compress into a smaller volume when pressure is applied. In a brake system, fluid pressure is multiplied by the master cylinder and can reach more than 1,000 pounds per square inch (psi) in the lines. Like any other hydraulic fluid, brake fluid must be non-compressible at the expected pressures to transmit force from one end of the system to the other while simultaneously lubricating the pistons and rubber parts as they move through their bores. If the fluid were to compress, all braking power would be lost. AMSOIL Brake Fluids remain non-compressible, even at the highest pressures generated in automotive brake systems. AMSOIL Brake Fluid provides superior stopping ability under the most demanding conditions.

Brake Fluid Maintenance

Brake fluid is vital to safe driving, yet one of the most neglected fluids in vehicles today. Experts recommend changing brake fluid every 12 to 24 months as preventative maintenance, even more often in wet and extremely humid climates. Many owner’s manuals recommend changing brake fluid every 24 months to remove moisture. Many European countries require regular brake fluid inspections; half of all cars fail.
     In the United States, half of all cars and light trucks that are 10 or more years old have never had their brake fluid changed. In addition, powersports applications such as motorcycles, ATVs and UTVs require routine brake fluid changes as well. After only a year of service, brake fluid in the average vehicle may contain as much as two percent water; up to three percent after 18 months. After several years of service, it is not unusual to find brake fluid contaminated by seven to eight percent water.
     Unlike other hydraulic fluids, brake fluid does not flow throughout the system. Brake fluid simply moves slightly back and forth for most of its life, leaving no opportunity to circulate through a heat exchanger of filter. Because it can't be filtered, brake fluid must hold contaminants in suspension to prevent corrosion and clogging of small passages.
     Changing brake fluid on a regular basis removes accumulated water and other contaminants, preserving the life of brake system components and increasing the performance and reliability of the brake system.

Applications