Hey guys, I am trying to see if it is O.K. to use Sythetic DOT4 brake fluid in place of the regular DOT3. I have read online people saying yes it is o.k. to mix, and NO do not mix. Because I am replacing my rear brake light switch, I was going to bleed the brakes. I bought some synthetic DOT4 earlier this year that is sealed, but I was not sure if I should use it, or just buy Regular DOT4. Thank you for your help.
Regards, Paul

All DOT3, DOT4 and DOT5.1 brake fluids can be mixed, synthetic or otherwise. But never mix anything with DOT 5. In fact most brake systems aren't designed for DOT5. The synthetic formulas have higher boiling points and are less hygroscopic. I've been using synthetic fluid for the last 3 or 4 years.

Thank you Derek. I appreciate the help!
Cheers Paul

yes all fluids are compatible except dot 5, dot 5 is silicone and not to be mixed

dot 5 is not the same as dot 5.1

I agree.
du907

By the way, I saw that you are in TN. If you ever need their services, Frame Straight out of Friendship TN (I think) is the best. I used them to straighten my forks and front wheel. First class job, I mean the wheel wasn't that true brand new. I highly recommend them.

Thank you DU907. I appreciate the info. I hope you all have a great weekend!
Cheers Paul