机油5w40 和 5w30 的区别,w 什么意思(What's the difference between 5w40 and 5W30 in Oil w) 机油 5w40 和 5w30 的区别,w 什么意思(What's the difference between 5w40 and 5W30 in Oil w) What's the difference between "5W40" and "5W30"? "W"? Grade index The grade index of oil ...