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DOT 5 Brake Fluid Be Used Instead of DOT 3 or 4?
refer to vehicle owner's manual for what the manufacturer recommends
or warns against. As a rule, vehicles equipped with anti-lock brakes
(ABS) should not use DOT 5 brake fluid.
5 brake fluid is silicone based. DOT 3 (standard) and DOT 4 (heavy-duty)
are glycol-based. It can be distinguished from conventional brake fluids
by its purple color (which comes from a dye).
does not absorb moisture. DOT 5 brake fluid does not become contaminated
with moisture over time as conventional DOT 3 and 4 brake fluids do.
Silicone is also chemically inert, nontoxic and won't damage paint like
conventional brake fluid. It also has a higher boiling point.
of this, it is often marketed as a premium "lifetime" brake
fluid. It is often used to preserve brake systems in antique vehicles
and those that sit for long periods of time between use.
5 silicone brake fluid is also very expensive (costing four to five
times as much as ordinary brake fluid), and it won't mix with glyco-
based brake fluid (creating concern over sludging if all old fluid isn't
removed when a system is refilled with silicone).
also has slightly different physical properties and compressibility,
making it unsuitable for ABS systems calibrated to work with DOT 3 or
4 brake fluid.