There are three basic types of brake fluid: DOT 3, 4, and 5. DOT 3 and 4 are glycol (mineral) based, while DOT 5 (far right) is silicone based. Always read the manufacturer's directions when selecting brake fluid. Not all DOT 3 and 4 fluids are the same. Some have special performance-improving additives that enable them to cope better with heat and moisture issues.