DOT 5 is the onlybrake fluid recommended to be used in Harley-Davidsons. I understand that it has a higher boiling point than other fluids.
Under no circumstances whatsoever should you mix DOT 5 with any other brake fluid, and furthermore I would never use it in any system which had previously had another grade in it, without a total strip and rebuild.
It also seems to be horrendously expensive compared with other grades. Over here in the UK we also have DOT 5:1 which is a totally different fluid to DOT 5.
