What type of brake fluid is typically used in vehicles?

The correct answer is that DOT 3, DOT 4, or DOT 5.1 brake fluids are typically used in vehicles. These designations refer to various types of hydraulic brake fluids that meet specific performance standards set by the Department of Transportation (DOT).

DOT 3 fluid is a glycol-based fluid that absorbs moisture, which can lead to decreased performance over time, but is widely used due to its cost-effectiveness. DOT 4 has a higher boiling point compared to DOT 3 and is often recommended for vehicles that require better performance, especially under high-stress conditions like racing or heavy loads. DOT 5.1 is also glycol-based and is formulated for high-performance applications, offering superior moisture absorption properties and boiling points, making it suitable for a wide range of vehicles, particularly those that may operate under extreme conditions.

In contrast, the other options refer to fluids that are not typically used for brake systems. SAE 30 or 40 are designations for motor oils, which do not provide the necessary hydraulic properties for brake systems and can lead to brake failure if used. ATF (Automatic Transmission Fluid) types A or B are used in automatic transmission systems and lack the appropriate characteristics needed for brake function. Mineral oil is not commonly