Brake Fluid Type-Question

[rychi1]

I have my brake lines done and I am ready to bleed the system. I bought some Prestone synthetic brake fluid but when I got home I noticed that it says DOT 3/4 synthetic brake fluid, not just DOT 3, which is what the manual recommends. After the recent post about mixing brake fluids being a major issue, I want to make sure I get the right thing. From what I can tell online the only difference is boiling point and given the proximity to exhaust, I would assume I am better off with DOT 4, but I trust the people here more than my google research so...

What kind of brake fluid should I get, DOT 3 or DOT 4?

[GoDadGo]

I'm using the DOT-4 since it has a higher boiling point and is required at our local Track.

https://nolamotor.com/

My bike also uses DOT-4 as the standard brake fluid and it's just a cruiser.

[NAZ]

In your case I doubt you'll see any issues using the DOT-3/4 synthetic brake fluid. It's good to be cautious as not all brake fluids are created equal. DOT-5 is a silicone based fluid and while superior in many ways to the poly-glycol based DOT-4 and lower fluids, it does not play nice with some elastomers and will not mix with DOT-4 and lower rated fluids. Then there is a DOT 5.1 that can mix with poly-glycol based fluids. So many choices -- makes it complicated. So when in doubt, it's usually safer to go with the stuff the owner's manual recommends.

Also, buy brake fluid in small bottles and don't keep opened bottles around if you're not going to use them right away. Poly-glycol based fluids are hygroscopic and will absorb water vapor from the air. This lowers the boiling point and raises the freezing point which is a bad thing. So limit the exposure to air and toss those open bottles that get stored in a shop cabinet out of sight and out of mind.

[rychi1]

Thank you for the advice.