Dot 3 --> Dot 4 Brake Fluid

[JayJay]

My Aerodeck specifies using "Dot 3 brake fluid only" on the reservoir,

I'm always a bit skeptical when I read something like that, because what if there wasn't any higher specced oil when that was specified? So it'd be like ours saying "use only Dot 3 or 4" now, because 5 isn't suitable and 5.1 wasn't around then (I have no idea if it was or not though).