DOT 3 absorbes the moisture in the brake lines. When your vehicle sits for long periods of time, the moisture attracted to the wheel cyclinders, etc., and that is what corrodes them so bad.
DOT 5 works to remove air from the brake system. It is probably better for long storage times because it attracts less moisture.
The rubber components have to be compatible for the fluid you use. The white and yellow paint markings on the rubber components in a new kit help determine whether it is compatible with DOT 3 and/or DOT 5.
