DOT 5 is silicone based. DOT 3 and 4 are glycol based. Do not attempt to "flush" a system that had DOT3/4 with DOT 5. The two are not miscible and have significantly different specific gravity,and there is no way that the glycol fluid can be compelete purged by flushing. The only way to change over to DOT 5 is to take the system completely apart and start with everything new, clean, and dry, then assemble all the hydraulic components with DOT 5. The lines should be thoroughly flushed with denatured alcohol and dried and the hoses replaced.

The advantage of DOT 5 is that it does not absorb water, so it need not be flushed as often, but DOT 5 is also NOT RECOMMENDED for ABS systems.

Duke