40 Cov Lus Qhia Txog Saw Hlau Hnav

Kev Piav Qhia Luv:

1. Nrog rau kev ua haujlwm ntawm tus kheej lubricating, thaum txoj kab xa khoom qhuav, nws ua rau kev xa khoom ceev ceev tau
2. Nws muaj kev sib txhuam coefficient tsawg heev
3. Txo qhov nro ntawm lub phaj saw hlau
4. Ua kom koj lub suab qis qis
5. Ua kom lub phaj saw hlau ntev dua, thiab yuav tsis ua rau puas tsuaj thiab khawb rau phaj saw hlau
6. Txo kev siv hluav taws xob