Final answer:
The synthetic type of brake fluid is DOT 5, which is silicone-based and non-hygroscopic, making it more stable over wide temperature ranges and suitable for vehicles not used frequently.
Step-by-step explanation:
The type of brake fluid that is synthetic is DOT 5. DOT 3 and DOT 4 fluids are glycol-based, whereas DOT 5 is a silicone-based brake fluid. DOT 5 brake fluid is not hygroscopic, which means that it does not absorb water like glycol-based fluids do.
This characteristic makes it more stable over a wider range of temperatures and is beneficial for vehicles that are not used frequently, as it will not absorb moisture over time.
However, it is important to note that DOT 5 brake fluid is generally not compatible with the ABS brake systems found in many modern vehicles and should not be mixed with other types of brake fluids.