DOT 5.1 is a type of brake fluid that is commonly used in vehicles, particularly those with high-performance braking systems. It is glycol-based and has a higher boiling point than standard DOT 3 and DOT 4 fluids, making it suitable for applications where brakes may heat up significantly. This characteristic helps prevent brake fade, ensuring reliable braking performance. Unlike DOT 5, which is silicone-based and not compatible with glycol-based fluids, DOT 5.1 can be mixed with DOT 3 and DOT 4. It is important to check compatibility before mixing fluids, as using the wrong type can lead to brake system failure.