INTERNAL COMBUSTION ENGINE

The present invention has an object to provide an internal combustion engine in which abnormal combustion accompanying inflow of oil hardly occurs. For this purpose, in one mode of the present invention, the internal combustion engine includes a plurality of cylinders disposed along a flow of cooling water, and a surge tank having a plurality of air outlet ports connecting to the respective cylinders, wherein the surge tank is formed so that relatively much oil accumulates in a vicinity of an air outlet port connecting to a cylinder which is located at an upstream side of the flow of the cooling water, and accumulation of the oil is relatively small in a vicinity of an air outlet port connecting to a cylinder which is located at a downstream side of the flow of the cooling water.