DOT 5 brake fluids are silicon fluid, and it is used in most modern cars. It is more expensive compared to others since it has a high bylining point. It has a dry boiling temperature of 356 degrees. Most of the new brake rotors are thin and small, and thus they disperse a lot of heat. This silicon-based brake fluid is ideal for this type of car since it can withstand high temperatures. The Federal Motor Vehicle Safety Standards (FMVSS) under FMVSS Standard No. 116 [5] defines grades DOT 3, DOT 4, DOT 5 and DOT 5.1, where DOT refers to the U.S. Department of Transportation. These are widely used in other countries. Their classifications broadly reflect the SAE's specifications, DOT 3 is equivalent to SAE J1703 and ISO class 3, DOT 4 to SAE J1704 and ISO class 4, etc. [6]

DOT 3 brake fluids are petroleum/non-mineral based, non-silicone, and fully synthetic brake fluids designed for use in a wide range of clutch and brake applications. It is made by mixing alcohol and glycerin. The brake fluid is based on polyethylene glycol ether technology for high performance. Then you can connect everything and run your car with the DOT 5 brake fluid. This is a long procedure so you should think twice before you decide on this step. Since you can just get a DOT 5.1 which performs almost the same as the 5. Conclusion This means that it is rather different from the regular hydraulic fluid that is known as ATF or transmission fluid. The fluid was a low viscosity fluid based on diluted alcohol. [11] 49% alcohol 49% distilled water 1% triethanolamine phosphate ( surfactant) 1% sodium mercaptobenzothiazole ( stenching agent) Characteristics [ edit ] DOT5 : DOT5 brake fluid has a dry boiling point of 260 degrees Celsius and a wet boiling point of 180 degrees Celsius.

The advantage of the silicon based DOT5 fluid is that it absorbs no moisture whatsoever, unlike the glycol-based fluids. Because it is also chemically inert it won't react with other chemicals in your braking system, nor will it even react to your car's paint which the glycol-based fluids will. For that reason,DOT5 fluid is also preferred for vintage and antique cars that don't get driven around a lot. It can be left to sit in the system arguably for the life of the car without causing any problems.

It also offers strong corrosion protection and resists absorbing moisture, so your brakes will stay in top-notch condition for longer. DOT-5.1 brake fluid from Liqui Moly also has extremely low compressibility, making it the perfect solution for racing and high-performance applications where precision is paramount. This discussion comparing the DOT 3, DOT 4, and DOT 5 brake fluids will help you to make the right decision on the one to use on your vehicle. The answer is no – mixing different brake fluids is not recommended. As DOT 5.1 is silicone-based, mixing with standard glycol-ether fluid (DOT 3 or 4) can cause severe damage and compromise the performance of your brakes. Mixing dot 5.1 with other silicone-based fluids (DOT 5) may be safe. However, this should be avoided unless prescribed by the manufacturer. Final Thoughts About Dot 5.1 Brake FluidToday, cars are commonly equipped with ABS, and DOT5.1 fluid is used since the viscosity of it helps the ABS work consistently even in cold climates. DOT 3 fluid needs to be changed every year, with DOT 4 and DOT 5.1 every second year. By doing this, you will prevent water contamination and debris from shortening the life of the whole braking system. The thing to note is that the dry boiling temperature is the temperature when we consider using DOT 3 from a new container. Meaning that this fluid is totally fresh. While the wet boiling temperatures are when this fluid is diluted with water.

Another con when it comes to this type of fluid is that it cannot be mixed with glycol-based fluids because it will not mix with them and also not deliver the performance you desire when you do so on your car. DOT 5 does have its applications. If you own an extremely rare car that has expensive or original paint, DOT 5 is the fluid for you because it will not eat away the paint if spilled. But, if you use DOT 5, you are almost required to bleed the brakes before you go for a spin. Why? DOT 5 is lighter than water. Any moisture will pool at the lowest point which is typically the calipers or wheel cylinders. Many classic cars have been lost after the owner decided to shake loose the cobwebs before bleeding the brakes. Remember, these are only the minimum standards. Brake fluid manufacturers can and often do improve on these figures and it is possible to find DOT 4 brake fluid with a higher boiling point than some DOT 5.1 fluids on the market. DOT 5 is a silicone-based fluid and is separate from the series of DOT 2, 3, 4, 5.1. It is immiscible with water, and with other brake fluids, and must not be mixed with them. Systems can change fluid only after a complete system changeover, such as a total restoration.DOT 5 brake fluid is a silicon-based fluid . This was developed to be used in cars where moisture was definitely going to be prevalent and unavoidable. That means things like high performance vehicles and military vehicles. It has a very high boiling point, but it also has more compressibility than the glycol ether-based fluids. Also, there are now DOT4 brake fluids that have boiling points that are actually above DOT 5 brake fluid so there aren't a lot of reasons for you to look into getting a DOT 5 fluid for your car if you don’t need it. DOT5 brake fluid is especially good at maintaining efficacy during very high temperatures and is completely immune to water in the brake lines. This makes it an attractive choice for any driver. However, if your car is not designed to handle silicone-based brake fluids then it can cause more harm than it fixes if you add it to your system. The main difference between these two brake fluids is in their boiling points. Part of the standards that need to be met by the manufacturers of DOT fluids are the minimum dry and wet boiling points. These are the minimum temperatures that the brake fluid must perform at before the brake fluid starts to boil, which can lead to complete brake failure.