the oil reservoir 10 when the piston 1 then runs through the upper dead center thereof during the operating cycle and very high accelerations occur because of the change in direction of the piston movement the oil previously accommodated in the oil reservoir 10 is held out of the splash holes 14 on to the facing lower side of the piston head 2 the oil reservoir 10 here forms a shaker space the shaking movements of which are used for ejecting the oil in a preferred embodiment some and preferably all of the splash holes are arranged with respect to the connecting rod zenith on that side of the shell part 11 which faces away from the inlet opening 13 as viewed in a circumferential direction about the axis of articulation of the connecting rod 8 alternatively or additionally the size of two or more splash openings 14 in the shell part 11 along a u shaped longitudinal axis can increase at an increasing distance from the inlet opening 13 for this purpose the shell part 11 has at least one first and one second splash opening 14 wherein the second is larger than the first and is further away than the first from the inlet opening 11 by means of the two measures the majority of the oil is ejected via the splash openings 14 precisely where the oil is most urgently needed for cooling namely on that side of the connecting rod which faces away from the splash jet the cooling of that part of the piston head 2 which faces away from the splash nozzle 15 is thus improved in a targeted manner since during pure splash cooling the remote regions always obtain less cooling oil at an increasing distance from the.