There was some discussion about this somewhere, and the fact that 1980’s brake systems should stick with what they are designed for, which I think is Dot3 isn’t it? Dot 4 absorbes moisture less quickly than Dot 3 but is the same Poly-glycol based fluid, so in that sense
it might not make much difference.
The Silicone based DOT5 is quite different and could damage seals or hoses it’s not designed for.
Better stick with DOT3 or DOT 4 I’d say.