What is the best indicator that a bearing is being properly lubricated?

The best indicator that a bearing is being properly lubricated is the oil temperature indicated by the bearing thermometer. Proper lubrication of a bearing is essential for its operation, as it reduces friction, helps dissipate heat, and prevents wear. Monitoring the oil temperature provides direct insight into the lubrication conditions within the bearing. If the temperature is within the normal operating range, it generally indicates that the lubricant is effectively reducing friction and that the bearing is being well-lubricated.

High temperatures may suggest inadequate lubrication, leading to increased wear and potential failure, while excessively low temperatures might indicate over-lubrication or ineffective lubricant circulation. Therefore, keeping an eye on oil temperature is crucial for ensuring that the lubricant is functioning as intended.

While other options like vibration levels, oil pressure readings, and noise levels can provide additional information about a bearing's health, they do not exclusively indicate lubrication conditions. For example, vibration levels can be influenced by misalignment or wear, oil pressure readings can vary due to other factors in the lubrication system, and noise levels may indicate problems without directly reflecting lubrication adequacy. Thus, monitoring oil temperature is the most reliable method for assessing proper lubrication in bearings.