What brake fluid - Dot 3, 4, 5 or 5.1?

[440]

Looking at replacing the brake fluid in my cars and doing a bit of research on the different types. There is a lot of praise for dot 5 being silicone based but there is also quite a bit of negative feedback as well. Dot 3 - 4 has been used for years and if changed every couple of years seems to be problem free.

Any opinions on dot 5.1, especially since being compatable with 3 - 4?

[tan top]

  stick with dot 4 ,  i personally would never use any kind of silicone brake fluid    ,
lots do though , & would never use anything else , & love the stuff 
, on the other side of the coin lots have had many many different  problems with silicone fluid ,  lots of our oem type rebuilt / repoped brake part , instructions i have seen  , even say warranty void if using silicone brake fluid & or dont use silicone brake fluid , !!  your choice  like i say many people use it with our kind of cars & brake hardware , & would not use anything else 

i would not , 

[440]

That's why 5.1 looks promising being glycol based. I might do just that tan top, flush with Dot 4 and be done with it if the others seem too iffy.

[Ghoste]

I've stayed with the Dot 4 in mine too.

[Dmichels]

Dot 4 is fine so is Dot 3 I use what ever I have around
Dave

[Fred]

Why change from Dot 3 or 4 when it's running trouble free?   If I were you, I'd leave well enough alone.
Why fix it if it's not broken?   

[Dino]

O'Reilly's dot 3.  It's been proven to work without issues for decades.  I see no reason whatsoever to change to something new.  I might as well dump a few bottles of snake oil in there.

[Musicman]

Just flush your system out every now and again, and replace with new fluid... That's it, no big deal 

[375instroke]

I've had DOT4 boil in the calipers, but that's at the track.  Will be using DOT5.1 next time.

[tan top]

I've had DOT4 boil in the calipers, but that's at the track.  Will be using DOT5.1 next time.

 boiled the brake fluid on a couple of disc braked cars on the street when i was younger , pretty scary feeling ,
wonder if drum brake cars take a longer or shorter time to cook the fluid under hard braking conditions    think hear transfer  to fluid is / would be quicker with cars with discs , maybe  , i'm no expert , just thinking out loud  

[A383Wing]

3 & 4 are basically the same, and you can mix them....anything above is not "compatible" with 3 or 4.....

If you change over to 5 or above, from what I have heard, everything with a rubber part has to be changed to new as well

I say stick with what works and had worked over the years....3 or 4

Bryan

[ODZKing]

Doing a search, I found this thread.  I have to replace the MC on my 73. I have had severl folks mention that I should convert to Dot 5 because it does not ruin paint (as some has dripped on my new paint under the hood and peeled).
I have not heard about the rubber ... is that true and what exactly would I have to change?   

[A383Wing]

if you change to 5, you will have to replace "everything" in the brake system that has rubber or seals in it.

front calipers or wheel cylinders, rear wheel cylinders, proportioning valve under car, master cylinder, all 3 brake hoses, and you also have to completely flush the remaining older fluid out.

[375instroke]

DOT 5.1 is not DOT 5.  DOT 5.1, like DOT 3 and DOT 4, is a polyethylene glycol-based fluid, whereas DOT 5 is silicone-based.