I had always thought you could put dot 4 into a dot 3 system but not the
other way around, however according to this:
'DOT 3 and DOT 4 fluids are mutually compatible, the major disadvantage of
such a mix being a lowered boiling point. In an emergency, it'll do.
Silicone fluid will not mix, but will float on top. From a lubricity
standpoint, neither fluids are outstanding, though silicones will exhibit a
more stable viscosity index in extreme temperatures, which is why the US
Army likes silicone fluids. Since few of us ride at temperatures very much
below freezing, let alone at 40 below zero, silicone's low temperature
advantage won't be apparent. Neither fluids will reduce stopping
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