Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (e.g. silicone/DOT 5 and mineral oil based formulations), are hydrophobic, and can maintain an acceptable boiling point over the fluid's service life. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol-based fluid (DOT 3/4/5.1) will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s. Silicone fluid is used extensively in cold climates, particularly in Russia and Finland.
我的07 Infiniti G35 service schedule上居然没半个字儿提到brake fuild change,除了premium service这个让dealer挣钱的东西，我的已经开了11万5,17年了一次也没换过，好奇之下想看看刹车油这么些年里到底吸了多少水进去，于是买了个brake fluid tester量量看
https://www.amazon.com/ITEQ-Liquid-Tester-Indicators-Calibrated/dp/B076SC377J/ref=sr_1_1?keywords=brake+fluid+tester&qid=1708046192&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1
一量居然说0% water. 哈
连续踩刹车时刹车液会发热到里面的水分沸腾的温度，水沸腾就产生气泡，气泡不同液体，能压缩，所以导致刹车变软。
所以有水分就要换，不幸的是刹车液吸水性极强，所以电马每三年就要换刹车液，不管你开了300迈还是3万。
14万迈时又换过一次前rotor和pads，下次到20万迈时就该前后rotor一起一起换了
最接近外界空气的地方不是密封的caliper而是只隔了一个可以打开的盖子的刹车液罐子，你说哪儿容易进水？
Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (e.g. silicone/DOT 5 and mineral oil based formulations), are hydrophobic, and can maintain an acceptable boiling point over the fluid's service life. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol-based fluid (DOT 3/4/5.1) will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s. Silicone fluid is used extensively in cold climates, particularly in Russia and Finland.