PS - If anyone has any additional information on different fluids, etc, please reply about it and I will add it up to this main post.
Common Brake Fluid Boiling Points
[u]Fluid Brand || W.B.P. || D.B.P.[/u](plagarism at it's best
Castrol SRF || 270°C || 310°C
Earl's HyperTemp 421 || 216°C || 307°C
Motul 600 || 215°C || 312°C
AP-600 || 210°C || 300°C
Neosynthetic 610 || 216°C || 321°C
ATE-Super Blue || 200°C || 280°C
Valvoline || 167°C || 267°C
Castrol LMA || 155°C || 230°C
Earl's HyperTemp 300 || 149°C || 298°C
Ford HD || 143°C || 288°C
Wilwood 570 || 140°C || 299°C
PFC-Z rated || 140°C || 288°C
AP-550 || 140°C || 288°C
* W.B.P. = Wet Boiling Point
* D.B.P. = Dry Boiling Point. _linenums:0'><strong class='bbc'>[u]Fluid Brand || W.B.P. || D.B.P.[/u]</strong> Castrol SRF || 270°C || 310°C Earl's HyperTemp 421 || 216°C || 307°C Motul 600 || 215°C || 312°C AP-600 || 210°C || 300°C Neosynthetic 610 || 216°C || 321°C ATE-Super Blue || 200°C || 280°C Valvoline || 167°C || 267°C Castrol LMA || 155°C || 230°C Earl's HyperTemp 300 || 149°C || 298°C Ford HD || 143°C || 288°C Wilwood 570 || 140°C || 299°C PFC-Z rated || 140°C || 288°C AP-550 || 140°C || 288°C * W.B.P. = Wet Boiling Point * D.B.P. = Dry Boiling Point.
)All brake fluids absorb moisture, some faster than others (except silicone which is not recommended for anti-lock brake systems). Castrol SRF resists moisture contamination (non-hygroscopic) more than any other fluid we tested, therefore change intervals can be greatly extended. This reduces the effective cost over a season of racing. Many drivers say that they can run the same fluid all year long with only bleeding off the fluid in the calipers for each event. This way a can or two will last all year. Other fluids (hygroscopic type) require additional flushing of the system for each track event to maintain the lowest percentage of moisture and the highest boiling point.
FYI - The Castrol SRF is around $130/container versus $30-50/container for the rest.
Silicone Brake Fluids
(more plagarism)
Fluids containing Silicone are generally used in military type vehicles and because Silicone based fluids will not damage painted surfaces they are also somewhat common in show cars.
Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver a feeling of a spongy pedal. The higher the brake system temperature the more the compressibility of the fluid and this increases the feeling of a spongy pedal.
Silicone based fluids are non-hygroscopic meaning that they will not absorb or mix with water. When water is present in the brake system it will create a water/fluid/water/fluid situation. Because water boils at approximately 100º C, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake systems performance.
MINIMAL boiling points for these specifications are as follows:
DOT # || Dry Boiling Point || Wet Boiling Point [/u]Poly Glycol Ether Based Brake Fluids
DOT 3 || 205ºC || 140ºC
DOT 4 || 230ºC || 155ºC
DOT 5 || 260ºC || 180ºC
DOT 5.1 || 270ºC || 191ºC _linenums:0'>[u] <strong class='bbc'>DOT # || Dry Boiling Point || Wet Boiling Point </strong>[/u] DOT 3 || 205ºC || 140ºC DOT 4 || 230ºC || 155ºC DOT 5 || 260ºC || 180ºC DOT 5.1 || 270ºC || 191ºC
(more plagarism)
Fluids containing Poly glycol ethers are regarded as DOT 3, 4, and DOT 5.1. These type fluids are hygroscopic meaning they have an ability to mix with water and still perform adequately. However, water will drastically reduce the boiling point of fluid. In a passenger car this is not an issue. In a racecar it is a major issue because as the boiling point decreases the performance ability of the fluid also decreases.
Poly glycol type fluids are 2 times less compressible than silicone type fluids, even when heated. Less compressibility of brake fluid will increase pedal feel. Changing fluid on a regular basis will greatly increase the performance of the brake system.
FLUID SPECIFICATIONS All brake fluids must meet federal standard #116. Under this standard is three Department of Transportation (DOT) minimal specifications for brake fluid. They are DOT 3, DOT 4, and DOT 5.1 (for fluids based with Polyalkylene Glycol Ether) and DOT 5 (for Silicone based fluids).
Wet vs. Dry Boiling Point
(more plagarism)
WET BOILING POINT - The minimum temperatures that brake fluids will begin to boil when the brake system contains 3% water by volume of the system.
DRY BOILING POINT - The temperatures that brake fluid will boil with no water present in the system.
How does water get in there?
(more plagarism)
Water/moisture can be found in nearly all brake systems. Moisture enters the brake system in several ways. One of the more common ways is from using old or pre-opened fluid. Keep in mind, that brake fluid draws in moisture from the surrounding air. Tightly sealing brake fluid bottles and not storing them for long periods of time will help keep moisture out. When changing or bleeding brake fluid always replace master cylinder caps as soon as possible to prevent moisture from entering into the master cylinder. Condensation, (small moisture droplets) can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers, lines, master cylinders, etc. When this water reaches 100º C the water turns to steam. Many times air in the brake system is a result of water that has turned to steam. The build up of steam will create air pressure in the system, sometimes to the point that enough pressure is created to push caliper pistons into the brake pad. This will create brake drag as the rotor and pads make contact and can also create more heat in the system. Diffusion is another way in that water/moisture may enter the system.
Diffusion occurs when over time moisture enters through rubber brake hoses. The use of hoses made from EPDM materials (Ethlene-Propylene-Diene-Materials) will reduce the amount of diffusion OR use steel braided brake hose with a non-rubber sleeve (usually Teflon) to greatly reduce the diffusion process.
DOT what?
(even more plagarism)
DOT: Acronym for "Department of Transportation" -- an American federal agency or "Department of Transport" -- a British agency
DOT 3: This brake fluid has a glycol base. It is clear or light amber in color. Its dry boiling point is 205°C minimum and wet boiling point of 140°C minimum. It will absorb 1 to 2 percent of water per year depending on climate and operating conditions. It is used in most domestic cars and light trucks in normal driving. It does not require cleaning the system and it can be mixed with DOT 4 and DOT 5.1 without damage to the system. The problem with it is that it absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.
DOT 4: This brake fluid has a borate ester base. It is clear or light amber in color. Its dry boiling point is 230°C minimum and wet boiling point of 155°C minimum. It is used in many European cars; also for vehicles in high-altitude, towing, or high-speed braking situations, or ABS systems. It does not require cleaning the system and it can be mixed with DOT 3 without damage to the system. The problem with it is that it absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.
DOT 5: This brake fluid generally has a silicone base. It is violet in color. Its dry boiling point is 260°C minimum and has no wet boiling point in federal DOT 5 specifications. It is used in heavy brake applications, and good for weekend, antique, or collector cars that sit for long periods and are never driven far. It does not mix with DOT 3, DOT 4, or DOT 5.1. It will not absorb water and will not damage the paint on a vehicle. It is also compatible with most rubber formulations. The problem with it is that it may easily get air bubbles into the system which are nearly impossible to remove, giving poor pedal feel. It is unsuitable for racing due to compressibility under high temperatures. If as little as one drop of water enters the fluid, severe localized corrosion, freezing, or gassing may occur. This can happen because water is heavier and not mixable with silicone fluids. It is unsuitable for ABS.
DOT 5.1: This brake fluid has a borate ester base. It is clear or light amber in color. Its dry boiling point is 260°C minimum and wet boiling point of 180°C minimum. It is used in severe-duty vehicles such as fleets and delivery trucks; towing vehicles, and race cars. It can be mixed with DOT 3 or DOT 4 without damage to the system. It maintains higher boiling point than DOT 3 or DOT 4 fluids due to its higher borate ester content. It is excellent for severe duty applications. The problem with it is that it costs more than other fluids and there is limited availability. It also absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.
What causes a mushy pedal?
(some more plagarism)
DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers. It is not uncommon to have caliper temperatures exceed 93° C, and at 100° C, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel.
Also, many sources indicate that stock rubber brake lines can be a cause of a 'spongy' brake pedal.
[u]Other good links:
http://www.shotimes....brakefluid.html
