My 2002 XL1200 front brake needs flushing. On the MS cap it calls for DOT 5, is that silicon 5 or reg. 5

 

All DOT 5 is silicone. No such thing as "regular" DOT 5.

 

DOT 5.1 is not compatible with DOT 5 which is very confusing. As mentioned, DOT 5 is DOT 5.

 

As Chris G said, DOT 5 is different than DOT 5.1 and should never be mixed.

DOT 5.1 is compatible with DOT 4 and the primary difference being a higher wet and dry boiling point with 5.1. Also worth noting to use a high quailty fluid from an unopened container. Purchase only enough fluid required to complete the flush as necessary. DOT 4 and 5.1 absorb moisture from the atmosphere once the container is opened. After opening the container, it's likely that the fluid should be recycled after a couple of months on the shelf, even though it has not been used.

From Raybestos:

"DOT 3, DOT 4 and DOT 5.1 are glycol-based fluids. Glycol-based fluids are hygroscopic, meaning they absorb water over time. As moisture gets into the brake system, the boiling point of glycolbased fluid lowers" DOT 5 is a silicone based fluid and is hydrophobic. You can not simply drain the existing non DOT 5 systems and replace with DOT 5 because the fluids are not compatible.

Paul

 

Thanks guys