Quote Originally Posted by OakLeaf View Post
[hijack] Does anyone know why only Harleys use DOT5 brake fluid (which is not corrosive, unlike DOT4)? There must be something inferior about its performance or durability, or all vehicles would use it, right? [/hijack]
Here's a quote from this website:
"On the disadvantage side however, silicone fluid [DOT5] aerates easily. Harley-Davison, one of the sole current OEM users of silicone fluid, warns buyers to let the fluid sit at least an hour before using it. The trip home in the saddlebag is enough to aerate silicone brake fluid until it looks like a freshly poured soft drink. Silicone fluid is also slightly more compressible than glycol fluid, does not change color to tip the user to its moisture content, and worst of all, neither accepts or disperses moisture, making systems using it more corrosion prone, and requiring much more frequent fluid changes. Silicone brake fluid also lacks glycol fluid's naturally occuring lubricity, making it incompatible with the mechanical valving in some antilock braking systems."

Sorry if that was more than you wanted to know. I get all research-y when someone asks an intriguing question I don't know the answer to.