There are standards written that document what makes up different brake fluids. DOT 3, 4, 5 & 5.1 have their own specifications. There should not be any issues mixing one brand of DOT 4 with another, as long as the same standard was in place at the time that particular bottle was made. As I understand it, all DOT 3 & 4 today is synthetic.A friend of mine read in a Chilton's repair manual that you shouldn't mix brands of DOT4 brake fluid.
I don't see why it would make any difference as long as both brands are DOT4.
Anyone ever heard of this?
There are standards written that document what makes up different brake fluids. DOT 3, 4, 5 & 5.1 have their own specifications. There should not be any issues mixing one brand of DOT 4 with another, as long as the same standard was in place at the time that particular bottle was made. As I understand it, all DOT 3 & 4 today is synthetic.
That said, someone recently found a bottle labeled to indicate non-synthetic DOT 3 and a bottle of non-synthetic DOT 4 on a store shelf. Not sure whether this was old stock or just an old labeling system. DOT 3, 4 & 5.1 fluids are polyethylene glycol based. I am also not sure whether or not DOT 3 was polyethylene glycol based 15 years ago, but just not called synthetic.:shrug:
Ralph:The original question (paraphrased) was "Can DOT4 brake fluid from manufacturer X be mixed with DOT4 from manufacturer Y?
No one's life is in danger and no master cylinders were harmed in the making of this question. LOL. Some of you guys sure love drama though.
My friend is planning to bleed his brakes sometime this summer and the Chilton manual said not to mix DOT4 with any other DOT number (duh) and also not to mix it with another brand of DOT4. Kind of hard to not mix brands when the bike is bought used and you don't know what brand is in the bike now. Plus it sounds absurd to me that two different brands couldn't be mixed. That's why there are standards such as "DOT 4" in the first place. Still, I thought I'd ask the question on this board on the slim outside chance that there's some chemical reason not to mix brands.
Yes. That's the plan. Only asked because of what he read in the Chilton manual.Ralph:
By the time a batch of polyethylene glycol meets the DOT 4 spec, I suspect that it doesn't matter where the feedstocks came from - synthetic v. organic probably makes no difference.
However, your friend might note that the bike is used, and he'd likely be surprised by the amount of gunk that can languish unseen in your brake system. It doesn't take hardly any more time to refill the whole system instead of just bleeding it a bit. Do the whole thing with one brand of new fluid and sleep soundly at night.
I just don't get it translates to I don't actually understand it which causes you to fear doing it. If you understood it, you would realize that there is nothing wrong with it. Of course then you would get it.Why even consider jeopardizing your life and bike performance over a $5.00+- product? I just don't get it? :shrug: