‘机油’ (jī yóu) literally combines ‘机’ (jī), meaning ‘machine’ or ‘engine’, and ‘油’ (yóu), meaning ‘oil’. Together, it specifically refers to engine oil—the lubricating fluid used in internal combustion engines to reduce friction, cool components, and prevent wear. It is essential for maintaining vehicle performance and longevity.

This term is used almost exclusively in mechanical, automotive, and maintenance contexts. While ‘油’ alone can mean many types of oils (e.g., cooking oil, vegetable oil), adding ‘机’ restricts the meaning to engine-related oil. You’ll commonly see it on service reminders, auto parts labels, mechanic discussions, and owner’s manuals. It is not used metaphorically or in daily household contexts unrelated to machinery.