Why must you ensure the brake fluid is changed regularly in accordance with the vehicle manufacturer's instructions?

To ensure that the braking system functions effectively, it is essential to regularly change the brake fluid as per vehicle manufacturer instructions. There are three key reasons why this is crucial:

1. **Function Under Load**: Brake fluid is vital for the braking system's operation, especially when the system is under high load, such as during heavy braking or driving in hilly areas. Old fluid can lose its effectiveness, compromising braking performance.

2. **Water Proportion**: Brake fluid can absorb moisture over time, increasing the water content, which can lead to vapor lock and decreased braking efficiency. Keeping the water level below the permitted threshold helps maintain safe braking conditions.

3. **Preventing Damage**: Degraded brake fluid can corrode and damage various components of the braking system. Regularly changing the fluid can help extend the life of these parts and ensure optimal performance.

According to German traffic regulations, maintaining optimal vehicle safety includes ensuring reliable braking performance, which makes regular brake fluid changes a legal and safety necessity. Understanding these aspects underscores the importance of selecting all relevant options regarding brake fluid maintenance.