hi heck- you illustrate one of the problems in obtaining accurate complete info on car stuff. the reason i just discovered for dot 4 brake fluid is higher boiling point. my volvo owners manual specifies dot 4 only. prestone and valvoline dot 4 plainly state meets higher temp standard. nothing about seals. both of these dot 4 products are as clear and colorless as dot 3. are you convinced better seal protection for the girling cylinders is indicated by the color of the oe fluid? thanks tons oldduke ps- may be a remote risk if you are right about the meaning of the color that i will yet be stuck with leaking brake seals in stinking creek, md. at 2. b/c i added prestone dot 4. bet it will be snowing like hell too.