Harley Davidson® Motorcycles specifies use of DOT 5 Silicone brake fluid because of its minimized impact on painted surfaces. Wilwood disc brake calipers will work with either fluid, but never mix DOT 5 Silicone brake fluid with DOT 3 or 4 fluids.
Changing brake fluid on a regular basis is highly recommended and easily accomplished when changing brake calipers. DOT 3 and DOT 4 brake fluids are superior for general brake system use as well as high-performance applications. For best results, Wilwood Engineering recommends the use of Hi-Temp 570 DOT 3 brake fluid (P/N 290-0632) or EXP 600 Plus DOT 4 brake fluid (P/N 290-6209).