A cylinder liner for providing reduced oil carry-over in an air-assisted fuel injection system comprising an air compression piston wherein the cylinder liner and air compression system together in part define an air compression chamber, the cylinder liner comprising: an outer surface; and a plurality of projections on the outer surface; wherein the plurality of projections are arranged such that oil-laden air drawn up from an oil reservoir around the outer surface of the cylinder liner is forced into a labyrinthine path to increase the time the oil-laden air is in contact with the outer surface and increase the amount of oil adhering to the outer surface to minimize the amount of oil carry-over entering the air compression chamber.