While removing the hydraulic motor from the coulping assembly, make sure that the hydraulic motor keeps being vertical to the level of work table or ground as shown in the image below not to allow the coupling oil to spill out. If the coupling oil spilled out of the hydraulic motor or the coupling assembly, replace the coupling assembly with new one. (We do not recommend to add or change the coupling oil because the coupling oil's spec and fill ratio greatly effect the performance and durability of the coupling assembly.)