Castrol Brake Fluid DOT 4 is a Synthetic glycols and borate ester that achieves a higher boiling point and wet boiling point. Castrol Brake Fluid DOT 4 is designed for use in all brake systems, including DOT 3 and particularly those which are exposed to extreme conditions. As with all brake fluids which contain glycol ethers, care should be taken to avoid spilling this product on paintwork as it may have a damaging effect. In case of spillage, rinse the affected area with water immediately. Do not wipe.