What happens if brake fluid levels are not maintained?

Maintaining proper brake fluid levels is crucial for the overall braking system functionality. If the fluid levels are low, it can lead to air entering the brake lines, reducing the hydraulic pressure necessary for effective braking. This diminished pressure compromises the system's ability to transmit force from the brake pedal to the brake components. As a result, the vehicle may experience a decrease in braking performance, making it less responsive and potentially unsafe.

The other answer choices relate to different vehicle systems. Increased tire pressure does not directly correlate with brake fluid levels, nor does improved combustion efficiency or enhanced engine performance. These aspects pertain more to the engine and tire systems rather than the braking system, highlighting that maintaining brake fluid levels is specifically linked to braking performance.