DOT 4 Brake Fluid Warning
WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
When adding fluid to the brake fluid reservoir or to the clutch fluid reservoir, use only DOT-4+ brake fluid from a clean, sealed container. This polyglycol brake fluid is hygroscopic and absorbs moisture. Do not use fluid from an open container that may be contaminated with water. Brake fluid must not be contaminated with mineral oil. Improper or contaminated fluid could result in system failure, loss of vehicle control, and possible injury. Complaints because of, or defects caused by contaminated brake fluid will not be accepted by GM warranty.