11.3 Coarse Oil Separation The coarse oil separator is based on a labyrinth, through which air with oil from the crankcase are exhausted. Due to the air direction changes in the labyrinth, oil particles separate, and proceed through the oil return line in the cylinder block back into the oil sump. The return line only ends under the oil sump oil surface. 11.4 Fine Oil Separation Contaminated gases flow through the cylinder head into the fine oil separator. Then, they are first cleaned in the cyclonic separator. Separated oil proceeds from the fine oil separator through a separate line in the cylinder block back to the oil sump.