Cylinder liner

A cylinder liner comprising:

• an outer circumferential surface provided with a plurality of groups of annular grooves, wherein
• each of said groups of annular grooves has first and second longitudinal grooves communicating said annular grooves with each other, forming an outlet and an inlet, respectively, for cooling oil and disposed at locations spaced apart by 180.degree. in a circumferential direction, wherein
• said outlet communicates with said inlet in series in said adjoining groups of annular grooves, wherein
• a total sectional area of said annular grooves in each of said groups of annular grooves is decreased from a lower part toward an upper part in an axial direction of said cylinder liner, and wherein
• said outer circumferential surface has further a third longitudinal groove connected to a lower end of said first longitudinal groove forming the outlet of said lowermost group of annular grooves, a circumferential groove connected to a lower end of said third longitudinal groove, and a fourth longitudinal groove having an upper end connected to said circumferential groove and a lower end open, and said fourth longitudinal groove having the upper end connected to said circumferential groove and the lower end open, is disposed at a different circumferential position from said first and second longitudinal grooves in each of said groups of annular grooves.