Replacing single reservoir M/C with dual reservoir on four wheel drum system

they say dot3 from a sealed container because dot 3 (and 4) are hygroscopic, meaning they will absorb moisture when exposed to air.

you can switch to dot 5, but must flush the system throughly (i like to use denatured alcohol). there usually isn't a compatibility issue with seals, especially when using new components. however, i will note that dot 5 seems to find and exploit even the teeny-tiniest gaps in the system and results in leaks that sometimes isn't a problem with dot 3/4