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General Tech Brake Fluid

KVH

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Just trying to recall: Synthetic can be mixed with non-synthetic, and Dot 3 is preferred for TR4s but can be mixed with Dot 4? Right?
 
My original can of DOT 5 said just add it and bleed until purple squirts out. Many years, no problems, but you probably should take John's advice.
Bob
 
From Valvoline:

Brake fluids can be mixed only if the fluid that you add to the system belongs to a higher grade.

For example, a braking system that has a brake fluid DOT 3 specification can use a DOT 4 or a DOT 5.1 fluid. Also, a system with a DOT 4 can be topped up with a DOT 5.1 without bleeding the system.

However, never top up a DOT 4 system with a DOT 3 brake fluid. DOT 3 won’t be able to meet the temperature requirements because of its lower dry and wet boiling points.

Once again, do not mix DOT 5 with any other type of brake fluid because of its silicone-based composition.


 
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