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Author Message   Xodot Posted on Saturday, September 11, 2010 - 10:42 pm:        Someone here suggested a Motul brake fluid change made a nice (and cheap) brake upgrade so I stopped by my trusted shop and he gave me 5.1 to replace the 4 DOT stock fluid. Of course the labels all say to use only the 4. I was told the only difference is 5.1 has a higher boiling point than the 4 and is therefore "better". Can I use the 5.1 if I flush and replace all the fluid in the system? It's not going to mess up the seals etc is it?   Boogiman1981 Posted on Saturday, September 11, 2010 - 10:45 pm:        theory says you can but i've always wondered exactly what is the flushing agent   Xodot Posted on Saturday, September 11, 2010 - 10:52 pm:        flushing agent = the new fluid (I assume?)   Boogiman1981 Posted on Saturday, September 11, 2010 - 10:59 pm:        i'm guessing but with the reaction between the two seems that'd be kinda risky. the silicon mixed with mineral oil= goo   Xnoahx Posted on Sunday, September 12, 2010 - 12:56 am:        You could try mixing some dot 4 and 5.1 in a jar, that would show what happens with the two fluids. Maybe mineral spirits for the flush? That or you can go to your trusted shop and have them exchange the dot 5.1 for some motul dot 4 and save yourself the hassle   Rhard Posted on Sunday, September 12, 2010 - 10:40 am:        In the old days we used alcohol to flush the system. It also used to be said that the silicone brake fluid doesn't have the same feel and coagulates after time.   Avalaugh Posted on Sunday, September 12, 2010 - 12:46 pm:        Don't use silicone brake fluid, dot 5.1 is fine, dot 5 is silicone and do not use it !   Avalaugh Posted on Sunday, September 12, 2010 - 01:58 pm:        http://www.millersoils.net/1_downloads/literature/ general/Brake_Fluid.pdf   Rhard Posted on Sunday, September 12, 2010 - 02:58 pm:        Thanks for the info. Early Buells like my '97 M-2 came with DOT-5.   Xodot Posted on Sunday, September 12, 2010 - 03:37 pm:        Avalaugh, From your provided link: There are two main types of brake fluids. • DOT 3, DOT 4 and DOT 5.1 which are based on poly glycol compounds. • DOT 5, which is based on Silicone. Note the two types of fluid are not compatible and must not be mixed in a braking system. Therefore going from DOT 4 to DOT 5.1 is NOT a problem because they both based on poly glycol compounds. The 5.1 simply has a higher boiling point and is therefore "better" for track days. Thanks for the reference~ I had done some searching and have learned a little since my original post but this does answer my question conclusively. Cheers   Boogiman1981 Posted on Monday, September 13, 2010 - 01:23 pm:        sweet that is some good info   Skntpig Posted on Monday, September 13, 2010 - 01:30 pm:        You can also try Motul RBF600. Works great and has a much higher boiling point for Dot4

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