Brake fluids — essential characteristics Which of the following are fundamental requirements for an automotive brake fluid?

Introduction / Context:
Brake fluid transmits pressure, lubricates components, and must withstand extreme temperatures. Choosing the right fluid prevents vapour lock, corrosion, and seal failure.

Given Data / Assumptions:

• Typical DOT 3/4/5.1 glycol-ether fluids or DOT 5 silicone in special cases.
• Hydraulic brakes with rubber seals and mixed metals.
• Operating conditions include cold starts and repeated hard stops.

Concept / Approach:
High boiling point prevents vapour formation under heavy braking. Low viscosity ensures rapid valve actuation (ABS) and good flow at low temperatures. Chemical compatibility with elastomers and metals avoids swelling, softening, or corrosion.

Step-by-Step Solution:
Property 1: Dry and wet boiling points must exceed service temperatures.Property 2: Viscosity must remain within specification over wide temperature range.Property 3: Additive package must protect seals and metal parts from corrosion and wear.Therefore, the correct selection is “all of these”.

Verification / Alternative check:
Standards (e.g., DOT) specify minimum boiling points, viscosity limits, pH range, and corrosion tests, confirming all listed properties are required.

Why Other Options Are Wrong:
Any single property alone is insufficient; lacking one compromises safety or durability.

“None of these” is clearly false.

Common Pitfalls:
Mixing incompatible fluids (e.g., DOT 5 with DOT 3/4/5.1), ignoring fluid change intervals causing low wet boiling point, or using contaminated containers.

Final Answer:
all of these