What Brake Fluid To Run? Dot 3, 4, 5 or 5.1?

[HawkRod]

As I restore my car all my brake components are essentially new and empty, allowing me to change the type of fluid I will use. What do you guys recommend?

* Dot 3 is the old standby, but absorbs a lot of water and has a low boiling point (probably unimportant for me with a street car)

* Dot 4 has similar properties to Dot 3, but slightly higher temp capabilities.

* Dot 5 is silicone, so it doesn't absorb water or eat paint, but it does cause some spongy pedals and can be a pain with entrenched air. Also it is expensive.

* Not sure what the deal is with Dot 5.1, seems like it is an improved version of Dot 4.

My inclination is to use Dot 4. It is readily available and I know it will work well. Silicone stuff has its problems and Dot 5.1 might be hard to get a hold of.

So what is your opinion what I should use and why?

Thanks,

Hawk

 

[69Bee]

Dot 3 is for drum brakes, and Dot 4 is for disc brakes. They both absorb water , and should be flushed and changed every couple years or so. If you use Dot 5, the entire system has to be flushed to remove the regular fluids, or use all new components and lines. Personally, I would stick with Dot 4 fluid. Easily gotten, inexpensive, and works well when properly maintained.

 

[Car Nut]

Dot 3 is for drum brakes, and Dot 4 is for disc brakes. They both absorb water , and should be flushed and changed every couple years or so. If you use Dot 5, the entire system has to be flushed to remove the regular fluids, or use all new components and lines. Personally, I would stick with Dot 4 fluid. Easily gotten, inexpensive, and works well when properly maintained.

What he said!! :yes:

 

[Canyon707]

I have just installed disc brakes in my drag car and am supposed to use either dot 4 or 5.1 only. I took the master cylinter top of only to find that it may have never been cleaned. It was full of debris and who knows what. It may have never been cleaned..... Any way I cleaned it completely and blew out the lines. So I am getting ready to install new fluid and see how that works. I have never done this before but, before I hook up the lines I want to see good clean fluid comming out of the lines.

 

[HawkRod]

Thanks for the replies - I guess I will just go with Dot 4 then!

I have just installed disc brakes in my drag car and am supposed to use either dot 4 or 5.1 only. I took the master cylinter top of only to find that it may have never been cleaned. It was full of debris and who knows what. It may have never been cleaned..... Any way I cleaned it completely and blew out the lines. So I am getting ready to install new fluid and see how that works. I have never done this before but, before I hook up the lines I want to see good clean fluid comming out of the lines.

From my understanding, DOT 5.1 is similar in chemical makeup to Dot 3 and 4. It is DOT 5 (not 5.1) that is silicone based. You may not need to worry about having super clean lines if you are using 4 or 5.1...

Hawk

 

[mopar12372]

synthetic dot3 boiling point same or better than dot 4 can be mixed with 3 or 4

 

[Canyon707]

dot 5.1 is different than dot 5 I have heard that dot 5 on disc brakes the pedal is spongeee. Strange egineering says dor 4 or dot 5.1 only for its brakes.