What is Brake Fluid DOT4
Brake fluid labeled as Department of Transportation DOT 4 is made with 50 to 65% glycol ether base with 20-30 % Borate Ester to resist boiling. The boiling point of dry DOT 4 is 450°F and 311°F when wet. Those are higher boiling points than DOT 3, but DOT 4 absorbs water about 20% faster than DOT 3 fluid.
Are brake fluids interchangeable?
DOT 4 fluid can be used in a vehicle where DOT 3 is specified, but DOT 3 should never be used on a vehicle where DOT 4 is specified because the DOT 3 boiling point will be lower than the brake system’s minimum specifications.
DOT 5 fluid can never be used in vehicles rated for either DOT 3 or DOT 4
©, 2021 Rick Muscoplat
Posted on by Rick Muscoplat