為了保(bao)證(zheng)車輛能夠(gou)制動(dong)靈(ling)活(huo)、有(you)效、可靠安全行駛。制動(dong)液必(bi)須(xu)具(ju)有(you)一定(ding)的性(xing)能指(zhi)標。其中主(zhu)要有(you)薪(xin)度、氣(qi)阻溫度、氧化安定(ding)性(xing)和防腐性(xing)、橡膠溶脹性(xing)等。

1.薪(xin)度。制(zhi)動(dong)液(ye)必(bi)須有(you)合(he)(he)適(shi)的(de)高(gao)、低(di)(di)溫勃度，以適(shi)應車輛在不同(tong)季(ji)節(jie)和不同(tong)地(di)區行駛，適(shi)合(he)(he)冬、夏通(tong)用。如果(guo)制(zhi)動(dong)液(ye)在溫度太高(gao)時其(qi)赫度過低(di)(di)，則起不到潤滑作用，而(er)且密封性差容易(yi)出現(xian)滲(shen)漏；制(zhi)動(dong)液(ye)在溫度太低(di)(di)時其(qi)赫度過大，則在嚴寒地(di)區使(shi)用時流(liu)動(dong)性差，影響行車安(an)全。

2．氣(qi)(qi)阻(zu)(zu)(zu)溫(wen)度(du)(du)(du)。氣(qi)(qi)阻(zu)(zu)(zu)溫(wen)度(du)(du)(du)是制(zhi)(zhi)(zhi)(zhi)動液(ye)(ye)最重(zhong)要的性能之(zhi)一。由(you)于制(zhi)(zhi)(zhi)(zhi)動系統工(gong)作時(shi)(shi)，制(zhi)(zhi)(zhi)(zhi)動蹄(ti)片與制(zhi)(zhi)(zhi)(zhi)動鼓之(zhi)間不斷摩擦(ca)產生熱(re)量(liang)，部分傳給(gei)大(da)氣(qi)(qi)，部分傳給(gei)制(zhi)(zhi)(zhi)(zhi)動液(ye)(ye)，從而使分泵制(zhi)(zhi)(zhi)(zhi)動液(ye)(ye)溫(wen)度(du)(du)(du)逐(zhu)漸升高，當制(zhi)(zhi)(zhi)(zhi)動液(ye)(ye)開(kai)始汽化后就會失去(qu)制(zhi)(zhi)(zhi)(zhi)動能力，這時(shi)(shi)的溫(wen)度(du)(du)(du)即為氣(qi)(qi)阻(zu)(zu)(zu)溫(wen)度(du)(du)(du)。制(zhi)(zhi)(zhi)(zhi)動液(ye)(ye)的氣(qi)(qi)阻(zu)(zu)(zu)溫(wen)度(du)(du)(du)越高，使用越安全可靠。

3．氧(yang)化(hua)安定性(xing)和防腐性(xing)。在制(zhi)動(dong)系(xi)(xi)統(tong)中，制(zhi)動(dong)液的壓(ya)力反復(fu)增大或減小(xiao)，工(gong)作溫度(du)和壓(ya)力均(jun)較常規制(zhi)動(dong)系(xi)(xi)統(tong)高(gao)。因此，制(zhi)動(dong)液應具有(you)更強的抗氧(yang)化(hua)性(xing)能(neng)，以免產生膠(jiao)質、沉積物和腐蝕性(xing)物質。氧(yang)化(hua)安定性(xing)關系(xi)(xi)到(dao)制(zhi)動(dong)液的使用壽命。防腐性(xing)關系(xi)(xi)到(dao)制(zhi)動(dong)液對(dui)制(zhi)動(dong)系(xi)(xi)統(tong)材料的影響，也會影響制(zhi)動(dong)系(xi)(xi)統(tong)的使用壽命。

4．橡膠溶(rong)脹(zhang)性(xing)(xing)。橡膠溶(rong)脹(zhang)性(xing)(xing)是(shi)制(zhi)動液的重(zhong)要性(xing)(xing)能之(zhi)一。在使用中若制(zhi)動液對(dui)橡膠皮碗產生溶(rong)脹(zhang)，就會引起滲漏，使制(zhi)動壓(ya)力(li)下降，甚至制(zhi)動失靈而造成事故。