So what's the difference between DOT 3, DOT 4, DOT 5 and DOT 5.1 brake fluid? Every type of brake fluid has a specific boiling point and water absorbing quality. Here is a little help to decide which is best for you and your application.
DOT 3 is the most common type of brake fluid used in domestic cars and trucks. According to the Society of Automotive Engineers (SAE), DOT 3 can absorb 2 percent of its volume in water every year. Over enough time excessive moisture will cause corrosion in the brake system which can lead to issues like vapor-lock or a spongy pedal. DOT 3 401*F (205*C) 284*F (140*C)
DOT 4 is formulated for use by all vehicles, it has a higher boiling point than DOT 3 and it does not absorb moisture as fast. DOT 4 and DOT 3 are interchangeable; however it's best to avoid adding DOT 3 fluid to a system that already uses DOT 4. It's the preferred type of fluid used for street and high performance applications. DOT 4 446*F (230*C) 311*F (155*C)
DOT 5 (often referred to as synthetic brake fluid) is silicone-based, which means it does not absorb any moisture. Many rodders would use synthetic because it's not corrosive to paint or other brake components, which makes it great for preserving classic cars for long periods of time. But there are a few drawbacks to silicon-based fluids. They expand more when compressed, which can make the pedal feel spongy. Also, DOT 5 fluids cannot be mixed with any other type of brake fluid. DOT 5 will usually have a violet tint in color to distinguish it from DOT 3, DOT 4, and 5.1 fluids. DOT 5 500*F (260*C) 356*F (180*C)
DOT 5.1 is a non-silicone-based polyglycol that has a boiling point over 500 degrees. Unlike DOT 5, DOT 5.1 can be mixed with DOT 3 or DOT 4. Also, DOT 5.1 will usually have the highest rated boiling point, which is best recommended for severe duty and high performance applications. DOT 5.1 518*F (270*C) 374*F (190*C)
It’s never a bad idea to change your brake fluid every couple of years and try not to leave your reservoir cap off any longer than needed.
DOT 3 is the most common type of brake fluid used in domestic cars and trucks. According to the Society of Automotive Engineers (SAE), DOT 3 can absorb 2 percent of its volume in water every year. Over enough time excessive moisture will cause corrosion in the brake system which can lead to issues like vapor-lock or a spongy pedal. DOT 3 401*F (205*C) 284*F (140*C)
DOT 4 is formulated for use by all vehicles, it has a higher boiling point than DOT 3 and it does not absorb moisture as fast. DOT 4 and DOT 3 are interchangeable; however it's best to avoid adding DOT 3 fluid to a system that already uses DOT 4. It's the preferred type of fluid used for street and high performance applications. DOT 4 446*F (230*C) 311*F (155*C)
DOT 5 (often referred to as synthetic brake fluid) is silicone-based, which means it does not absorb any moisture. Many rodders would use synthetic because it's not corrosive to paint or other brake components, which makes it great for preserving classic cars for long periods of time. But there are a few drawbacks to silicon-based fluids. They expand more when compressed, which can make the pedal feel spongy. Also, DOT 5 fluids cannot be mixed with any other type of brake fluid. DOT 5 will usually have a violet tint in color to distinguish it from DOT 3, DOT 4, and 5.1 fluids. DOT 5 500*F (260*C) 356*F (180*C)
DOT 5.1 is a non-silicone-based polyglycol that has a boiling point over 500 degrees. Unlike DOT 5, DOT 5.1 can be mixed with DOT 3 or DOT 4. Also, DOT 5.1 will usually have the highest rated boiling point, which is best recommended for severe duty and high performance applications. DOT 5.1 518*F (270*C) 374*F (190*C)
It’s never a bad idea to change your brake fluid every couple of years and try not to leave your reservoir cap off any longer than needed.
