Constant level oilers are designed to supply lubricant, as needed, to maintain a constant level within a bearing housing. They replenish lubricant lost by leakage through seals, vents and plugs in the bearing housing. However, problems can arise when reverse flow to the oiler occurs. Bearings create currents and flows in the housing as the shaft rotates. The location of a constant level oiler relative to shaft rotation can affect how the oiler dispenses - especially in higher speed applications. On start-up, as the shaft rotates, it will pull the lubricant to one side of the bearing housing. The oiler should be mounted so that the lubricant is pushed towards the oiler. If it is mounted on the incorrect side, and the lubricant is pulled from the oiler, the oil level momentarily drops below the control point, causing the oiler to feed. Over the course of several start-ups, the lubricant level within the bearing housing will increase above the optimum level. In high-level operating conditions, the bearings will require additional energy to go through the high-level lubricant. This energy converts to heat in the lubricant, causing it to lose its viscosity. In addition, "churning" of the lubricant will occur, accelerating the oxidation rate as a result of the excessive air and heat. The most common fix for this condition is to mount the oiler on the opposite side or on the bottom of the housing to eliminate mis-feeding due to currents created by the bearings.