From Strange dated August 26, 2021 - Master Cylinder page 1 of 3
Due to temperatures experienced during drag racing, DOT 4, DOT 5.1 or a high performance glycol based brake fluid is recommended. Brake systems are prone to moisture from humidity and regular use, therefore, moisture must be absorbed by the brake fluid instead of collected so the fluid does not easily boil.
DOT 5 (silicone based) is not recommended. It does not mix with other fluids. It is slightly compressible giving soft pedal/handle. It also does not absorb water. When moisture enters the system, it settles at the lowest point in which most cases is the caliper. At braking temperatures moisture can boil causing a loss or lack of pedal/handle.
Always perform a complete flush to the brake system when changing to a different brake fluid to avoid contamination. Do not use brake fluid from open bottles or bottles stored for long periods as moisture may have been absorbed. The dry boiling point is the temperature at which brake fluid will boil with no water (moisture) present in the system. The wet boiling point is the temperature at which brake fluid will boil when 3% is water by volume of the system.
In race applications it's assumed brake fluid is changed often therefore moisture is not present and the dry boiling point can be a better reference when deciding on which fluid to use.
DOT 3 Inexpensive, readily available, mixes with DOT 4 and DOT 5.1 Lowest boiling point, absorbs water, eats paint
DOT 4 Higher boiling point than DOT 3, absorbs water less readily than DOT 3 Absorbs water, eats paint
DOT 5 Does not eat paint, high boiling point Does not mix with water, difficult to bleed
DOT 5.1 High boiling point, mixes with DOT 3 & 4 Absorbs water, eats paint