Correction: My apologies for the confusion.
DOT 3 vs. DOT 4 Brake Fluid Differences (Can You Mix Them?)
What are the pros of the DOT4 brake fluid over the DOT3, and can you mix them? Let's find out!
The brake system is one of these things which are very important to take care of because you really want it to function properly in an emergency situation.
The brake fluid is one of these things that you need to replace every one or two years otherwise, it may cause rust inside the brake system and damage other parts.
There are two general types of brake fluids are produced: silicone or glycol basis. Dot3 and Dot4 are popular glycol-based brake fluid options available for many vehicles. While Dot3 is popular with normal drivers, Dot4 is more common in newer car models.
But what is the difference between them and can you mix them with each other?
Dot 3 vs. Dot 4 Brake Fluid Differences
The main differences between the Dot 3 and Dot 4 brake fluid are the boiling point. The Dot 4 brake fluid does have both a higher wet and dry boiling point and is better suited for higher performance.
Both Dot 3 and Dot 4 brake fluids are glycol-based products used in your braking system. They are hygroscopic and absorb water from the atmosphere, which means that care must be taken when storing and regularly replacing potentially contaminated fluids.
Type | Wet Boiling Point | Dry Boiling Point | Composition |
DOT 3 | 400°F/205°C | 285°F/140°C | Glycol Ether |
DOT 4 | 445°F/230°C | 310°F/155°C | Glycol Ether/Borate Ester |
DOT 5 | 500°F/260°C | 355°F/180°C | Silicone |
DOT 5.1 | 500°F/260°C | 355°F/180°C | Glycol Ether/Borate Ester |
Can you mix Dot 3 and Dot 4 Brake Fluid?
Yes, Dot 3 and Dot 4 brake fluid can be mixed. It’s because both these are glycol-based brake fluids, which means that they are compatible with each other. If your car has Dot 4 from the factory, it’s not recommended to fill it with Dot 3, though; but the other way is fine.
If you have Dot 3 in your car from the factory and you know that you are often driving with a trailer or in steep hills, we strongly recommend refilling it with Dot 4 instead.
Can you mix Dot 5 with dot 3 and dot 4?
Dot5 is a silicone-based brake fluid. It does not absorb water from the air and is not compatible with ABS systems. It maintains its integrity and works well. It also has a higher boiling point than the brake fluids Dot3 and Dot4, making it more compatible with excessively aggressive driving.
However, it is not compatible with Dot3 or Dot4 liquids and should never be mixed with them. You must also follow your manufacturer’s recommendations to know whether your braking system is compatible with Dot5 brake fluid.