What are the types of brake fluid?
2 Answers
Brake fluid, also known as automotive brake fluid, comes in three types: alcohol-based, mineral oil-based, and synthetic. Below is a detailed introduction to brake fluid: Alcohol-based: There are two grades: No. 1 and No. 3. Mineral oil-based: There are two grades: No. 10 and No. 15. Synthetic: Currently, the most widely used is synthetic brake fluid, which is further divided into three main types: glycol-ether-based, ester-based, and silicone-based. However, the most commonly used are glycol-ether-based and ester-based. Function of brake fluid: The role of brake fluid is to transmit braking pressure. High-quality brake fluid ensures both vehicle safety and the personal safety of drivers and passengers in emergency situations.
I remember checking the manual last time when changing brake fluid, and the main types are DOT 3, DOT 4, DOT 5, and DOT 5.1. DOT 3 is the oldest type, cheap but too hygroscopic with a low boiling point. It needs replacement every year or so, otherwise, the brakes feel spongy. Once I delayed it and almost rear-ended someone in city traffic. DOT 4 is more common and safer, with a higher boiling point, suitable for most family cars and can last two years without replacement. DOT 5 is silicone-based and doesn’t absorb water, which is good, but some vehicle systems aren’t compatible, and mixing it with old fluid can cause issues. DOT 5.1 has the highest boiling point, making it more reliable for highway downhill driving, though it’s a bit pricey. Always check the car manual for recommendations when choosing fluid—don’t switch types randomly. Increased water content can drastically lower the boiling point, which is very dangerous. Now I make sure to check it every two years, using a test pen to measure water content and replacing it promptly if it’s too high.
