為了保證車輛能(neng)夠(gou)制動靈活(huo)、有效、可(ke)靠(kao)安(an)全行(xing)駛。制動液必須具有一(yi)定的性能(neng)指(zhi)標。其中(zhong)主要有薪(xin)度、氣阻(zu)溫度、氧化安(an)定性和(he)防腐性、橡膠(jiao)溶脹性等。

1.薪(xin)度(du)。制動(dong)(dong)液必(bi)須有合適的高(gao)、低溫勃度(du)，以適應車(che)輛在不同季節和(he)不同地區行(xing)駛(shi)，適合冬、夏(xia)通(tong)用(yong)。如果制動(dong)(dong)液在溫度(du)太高(gao)時(shi)其赫(he)度(du)過(guo)(guo)低，則起不到潤滑作用(yong)，而且密封性差容易出(chu)現滲漏；制動(dong)(dong)液在溫度(du)太低時(shi)其赫(he)度(du)過(guo)(guo)大，則在嚴寒地區使用(yong)時(shi)流動(dong)(dong)性差，影(ying)響行(xing)車(che)安全(quan)。

2．氣(qi)阻溫(wen)度(du)(du)。氣(qi)阻溫(wen)度(du)(du)是制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)液(ye)最重要的性(xing)能(neng)之一。由于制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)系統工(gong)作時，制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)蹄片與制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)鼓之間不斷摩擦產生(sheng)熱量，部(bu)分(fen)(fen)傳給大氣(qi)，部(bu)分(fen)(fen)傳給制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)液(ye)，從而使(shi)分(fen)(fen)泵制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)液(ye)溫(wen)度(du)(du)逐漸升高，當(dang)制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)液(ye)開始汽化(hua)后就會(hui)失去制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)能(neng)力，這時的溫(wen)度(du)(du)即(ji)為氣(qi)阻溫(wen)度(du)(du)。制(zhi)(zhi)(zhi)(zhi)動(dong)(dong)液(ye)的氣(qi)阻溫(wen)度(du)(du)越高，使(shi)用越安全(quan)可靠。

3．氧(yang)化(hua)安(an)定性(xing)(xing)(xing)和防腐(fu)性(xing)(xing)(xing)。在(zai)制(zhi)動(dong)(dong)系(xi)(xi)(xi)統(tong)中，制(zhi)動(dong)(dong)液(ye)(ye)的(de)壓力(li)反(fan)復增(zeng)大(da)或減小，工作溫度和壓力(li)均較常規制(zhi)動(dong)(dong)系(xi)(xi)(xi)統(tong)高。因此，制(zhi)動(dong)(dong)液(ye)(ye)應具有更(geng)強的(de)抗氧(yang)化(hua)性(xing)(xing)(xing)能，以免產生膠質、沉積物(wu)和腐(fu)蝕性(xing)(xing)(xing)物(wu)質。氧(yang)化(hua)安(an)定性(xing)(xing)(xing)關(guan)系(xi)(xi)(xi)到制(zhi)動(dong)(dong)液(ye)(ye)的(de)使用(yong)壽命(ming)。防腐(fu)性(xing)(xing)(xing)關(guan)系(xi)(xi)(xi)到制(zhi)動(dong)(dong)液(ye)(ye)對制(zhi)動(dong)(dong)系(xi)(xi)(xi)統(tong)材料的(de)影響(xiang)，也會影響(xiang)制(zhi)動(dong)(dong)系(xi)(xi)(xi)統(tong)的(de)使用(yong)壽命(ming)。

4．橡膠溶脹性。橡膠溶脹性是(shi)制動液(ye)(ye)的(de)重要性能之(zhi)一。在(zai)使用(yong)中若制動液(ye)(ye)對橡膠皮碗產生溶脹，就(jiu)會引(yin)起滲漏，使制動壓力下降，甚至制動失靈而造成(cheng)事(shi)故。