Brake fluid should be changed every two years. When choosing, manufacturer‘s specifications must be observed because there are different classes: DOT 3, 4, 5 and 5.1 differ mainly in terms of boiling point and cold viscosity. DOT 3, 4 and 5.1 are glycol-based, DOT 5 silicone-based.
The higher the DOT class, the higher the boiling temperature and wet boiling point. Higher DOT classes tend to allow for longer maintenance intervals. The DOT standards are based on the American FMVSS-116 standard of the Department of Transportation (DOT).