Abstract: The present invention addresses the problem of providing a cylinder liner or a cylinder bore, which can reduce not only friction on a sliding surface but also oil consumption. In a piston sliding direction of the cylinder bore, grooves of a second sliding region positioned on the side of crankcase have a higher groove area ratio at a depth of 0.3 ?m than grooves of a first sliding region positioned on the side of combustion chamber, and the groove area ratio is in a specific range, whereby friction and oil consumption can be reduced.

Abstract: The present invention addresses the problem of providing a cylinder liner for insert casting, with which the bonding strength between a cylinder liner and a cylinder block can be improved by reducing voids generated on the cylinder block. The problem is solved by a cylinder liner for insert casting which includes plural projections on its outer peripheral surface and satisfies the following (i) and (ii): (i) the number of the projections is 5 to 50 per 1 cm2 on the outer peripheral surface, and (ii) when two 15.2 mm×0.03 mm lines are set in parallel with a gap of 3.8 mm therebetween at an arbitrary position on the outer peripheral surface of the cylinder liner, the total number of projections that are in contact with the two lines is 8 or less.

Abstract: An object of the present invention is to provide a cylinder liner for insert casting that can improve the joining strength between a cylinder liner and a cylinder block by reducing voids generated between the cylinder liner and the cylinder block. The above-described problem can be solved when the molten metal running index YI defined by the following Formula (1) is from 2.2 to 14.5. Molten metal running index YI=[area ratio St (%) of top portions of protrusions×molten metal infiltration volume V (mm3)/surface area A (mm2) of cylinder liner base]/average surface-to-surface distance Pav between top portions of protrusions (mm)??(1).