對于或由于混入水分而使脂的表面(mian)乳(ru)化變白(bai)等，這些現象(xiang)均表明(ming)潤滑(hua)脂已變質，不可(ke)使用。

　　聞(wen)氣味(wei)：如(ru)果打裝時(shi)聞(wen)到明顯的油(you)脂(zhi)(zhi)酸的臭味(wei)，表明潤滑脂(zhi)(zhi)已變(bian)質，不可使(shi)用。

　　手(shou)(shou)捻(nian)(nian)：用(yong)手(shou)(shou)捻(nian)(nian)不含填充劑的潤滑脂時(shi)，手(shou)(shou)感(gan)光滑，沒有硌(luo)手(shou)(shou)感(gan)；否則，則可能是稠(chou)化劑分散不均勻或混入雜質，這種(zhong)脂不可使用(yong)。但含填充劑粉(fen)末的潤滑脂略有硌(luo)手(shou)(shou)感(gan)。

　　用(yong)(yong)火燒：用(yong)(yong)鐵絲一塊潤(run)(run)滑(hua)脂(zhi)，然(ran)后用(yong)(yong)打火機燒，如果潤(run)(run)滑(hua)脂(zhi)軟化滴(di)(di)(di)落(luo)，表明是滴(di)(di)(di)點過(guo)低的劣質潤(run)(run)滑(hua)脂(zhi)，不可使(shi)用(yong)(yong)。需要(yao)說明的是，用(yong)(yong)這(zhe)種方法只能鑒別滴(di)(di)(di)點過(guo)低的劣質潤(run)(run)滑(hua)脂(zhi)，因打火機火焰(yan)的溫度不超過(guo)120~130℃，而大多數潤(run)(run)滑(hua)脂(zhi)的滴(di)(di)(di)點都超過(guo)了這(zhe)個溫度，用(yong)(yong)打火機燒都不會(hui)滴(di)(di)(di)落(luo)。

　　在(zai)陽光(guang)下(xia)曬(shai)：取(qu)一塊潤滑(hua)脂放在(zai)杯中在(zai)陽光(guang)下(xia)曬(shai)一兩天，如果脂體變化(hua)大(da)。

　　根據稠(chou)化劑可分為皂(zao)基(ji)脂(zhi)(zhi)和(he)(he)非(fei)皂(zao)基(ji)脂(zhi)(zhi)兩類。皂(zao)基(ji)脂(zhi)(zhi)的(de)(de)稠(chou)化劑常用(yong)(yong)(yong)(yong)鋰、鈉、鈣、鋁、鋅等(deng)金(jin)屬(shu)皂(zao)，也用(yong)(yong)(yong)(yong)鉀、鋇、鉛、錳等(deng)金(jin)屬(shu)皂(zao)。非(fei)皂(zao)基(ji)脂(zhi)(zhi)的(de)(de)稠(chou)化劑用(yong)(yong)(yong)(yong)石墨(mo)、炭黑、石棉(mian)還有(you)合成的(de)(de)（如聚(ju)脲基(ji)、膨潤(run)土），根據用(yong)(yong)(yong)(yong)途可分為通用(yong)(yong)(yong)(yong)潤(run)滑脂(zhi)(zhi)和(he)(he)專用(yong)(yong)(yong)(yong)潤(run)滑脂(zhi)(zhi)兩種，前者用(yong)(yong)(yong)(yong)于(yu)一般機(ji)械零件，后者用(yong)(yong)(yong)(yong)于(yu)拖拉機(ji)、鐵道機(ji)車、船舶機(ji)械、石油鉆(zhan)井機(ji)械、閥門等(deng)。主要(yao)質量指(zhi)標是滴(di)點、針入度、灰分和(he)(he)水分等(deng)。

　食品級潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)因此，對一(yi)(yi)些不可避免與有機(ji)溶劑接觸的(de)(de)(de)情況下，則(ze)應(ying)選用耐溶劑或耐汽油潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)油脂(zhi)，特別(bie)是(shi)在(zai)飛機(ji)或汽車等發動機(ji)燃油泵或某些汽油泵的(de)(de)(de)軸承(cheng)(cheng)上(shang)(shang)都應(ying)選用耐燃油潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)油油脂(zhi)。潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)在(zai)一(yi)(yi)開(kai)始進行了復雜的(de)(de)(de)流動后，就進入安(an)定分(fen)布狀態，遺(yi)(yi)(yi)留在(zai)摩擦部位(wei)的(de)(de)(de)少量流動性潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)起(qi)(qi)著主要(yao)的(de)(de)(de)潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)作用，而(er)遺(yi)(yi)(yi)留在(zai)外(wai)(wai)罩內(nei)(nei)(nei)的(de)(de)(de)潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)本身并不流動，即不起(qi)(qi)直接的(de)(de)(de)潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)作用。但是(shi)遺(yi)(yi)(yi)留在(zai)外(wai)(wai)罩內(nei)(nei)(nei)的(de)(de)(de)潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)起(qi)(qi)密封作用，以防止遺(yi)(yi)(yi)留在(zai)摩擦部位(wei)的(de)(de)(de)流動性潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)流出。可見潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)填(tian)充(chong)過多或不足(zu)，都會引起(qi)(qi)軸承(cheng)(cheng)溫(wen)度升高(gao)，不能保證軸承(cheng)(cheng)持續運行。一(yi)(yi)般的(de)(de)(de)潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)填(tian)充(chong)量可參考(kao)下面(mian)原則(ze)。一(yi)(yi)般軸承(cheng)(cheng)內(nei)(nei)(nei)不應(ying)裝(zhuang)滿(man)潤(run)(run)(run)滑(hua)(hua)(hua)(hua)(hua)脂(zhi)，以裝(zhuang)到軸承(cheng)(cheng)內(nei)(nei)(nei)腔(qiang)(qiang)全部空(kong)(kong)間(jian)的(de)(de)(de)二分(fen)之(zhi)一(yi)(yi)即可。水平(ping)軸承(cheng)(cheng)填(tian)充(chong)內(nei)(nei)(nei)腔(qiang)(qiang)空(kong)(kong)間(jian)的(de)(de)(de)三分(fen)之(zhi)二。垂直安(an)裝(zhuang)的(de)(de)(de)軸承(cheng)(cheng)填(tian)充(chong)腔(qiang)(qiang)內(nei)(nei)(nei)空(kong)(kong)間(jian)上(shang)(shang)側二分(fen)之(zhi)一(yi)(yi)。

　　潤(run)(run)滑(hua)脂(zhi)按稠(chou)化(hua)(hua)劑(ji)組成分(fen)(fen)類(lei)，局限性較大，使(shi)(shi)用(yong)(yong)(yong)(yong)同一種稠(chou)化(hua)(hua)劑(ji)可(ke)以生(sheng)產出許(xu)多(duo)種具有不同性能(neng)的潤(run)(run)滑(hua)脂(zhi)，即(ji)使(shi)(shi)是不同類(lei)型的稠(chou)化(hua)(hua)劑(ji)生(sheng)產的潤(run)(run)滑(hua)脂(zhi)，其性能(neng)也往(wang)往(wang)難(nan)以準確區(qu)分(fen)(fen)。所以，以稠(chou)化(hua)(hua)劑(ji)分(fen)(fen)類(lei)使(shi)(shi)用(yong)(yong)(yong)(yong)者會感(gan)到混淆不清(qing)，不依據使(shi)(shi)用(yong)(yong)(yong)(yong)經驗及查(cha)找(zhao)(zhao)對應標準就(jiu)難(nan)以選(xuan)用(yong)(yong)(yong)(yong)。從分(fen)(fen)組、命名和代(dai)號中看(kan)不出潤(run)(run)滑(hua)脂(zhi)的使(shi)(shi)用(yong)(yong)(yong)(yong)條件，必(bi)須(xu)再查(cha)找(zhao)(zhao)這個代(dai)號的潤(run)(run)滑(hua)脂(zhi)標準。因此(ci)，給使(shi)(shi)用(yong)(yong)(yong)(yong)者正確選(xuan)用(yong)(yong)(yong)(yong)帶(dai)來困難(nan)，容易發生(sheng)錯用(yong)(yong)(yong)(yong)，造成潤(run)(run)滑(hua)意(yi)外(wai)。