1. Cov cuab yeej siv tshuab tsis tuaj yeem pib: xyuas seb lub tshuab hluav taws xob txuas nrog, yog tias qhov kev nyab xeeb hloov pauv tau qhib, thiab yog tias muaj cov khib nyiab thaiv.
2. Qhov luaj li cas ntawm cov khoom ua tiav tsis ua raws li cov qauv: kho qhov ntev thiab lub sij hawm ntawm kev pub mis, hloov cov txheej txheem tsis, thiab lwm yam.
3. Pwm hnav lossis kev puas tsuaj: tsis tu ncua xyuas qhov hnav ntawm pwm, ntxuav nws tsis tu ncua, thiab yog tias muaj kev puas tsuaj lossis hnav hnyav, kho lossis hloov nws raws sijhawm.
4. Lub tshuab ua haujlwm qeeb qeeb: xyuas seb cov khoom puas yuav tsum tau hloov nrog cov roj lubricating, ntxuav nrog cov lus qhia, thiab lwm yam kom ntseeg tau tias cov khoom siv ruaj khov.
