Brake Fluid Question

[meangreenLXi]

I need to add brake fluid to my car and it says on the cap DOT3 OR DOT4 brake fluid. I'm not sure which one is in already and it says that you shouldn't mix, so how do I figure out which one to use. I got a whole bottle of DOT3 brake fluid and i'm not sure if I should put that in. :welcome: all help.

[shepherd79]

take a small sample from the car and mix it with the new one. this way you will see if anything happens to it.

[meangreenLXi]

so, mix it and see if it meshes or seperates, okay

[mouchyn]

well, actually, different types of brake fluid can chemically react and produce bubbles, foam, heat, water, and all kinds of other stuff. I don't think you have to worry about reactions like that until you get into DOT5 fluid and racing fluids.

[meangreenLXi]

sorry, posting from work and it timed out and resent last post.

[acranox]

DOT3 and DOT4 should mix okay. They are both Polyalkylene glycol fluids. DOT4 has a higher boiling point.
You can't safely mix DOT3 or DOT4 with DOT5.
If someone put DOT5 in your car I think that would have damaged the seals, and you've have an assortment of leaks in your system.

[meangreenLXi]

I just heard also that DOT3 is for regular honda usage and DOT4 is when you add a big brake kit or basically for high performance usage? Any truth to this???

[meangreenLXi]

Hey just found this! http://www.tccoa.com/brake-fluid/

[Strugglebucket]

anybody try valvoline synthetic brake fluid?

[meangreenLXi]

i just picked up some prestone synthetic from autozone

[DBMaster]

I have been using the Valvoline "synthetic" fluid for years. I have noticed that it is a lot cleaner looking when I flush it out for replacement every 30K miles as recommended by Honda. One could probably leave it in a little longer I suppose.

My master cylinder still seems to develop piston seal leaks about every 100K miles, regardless.