What should a plane journal bearing operating at slow speed be lubricated with?

A plane journal bearing operating at slow speed should be lubricated with oil that has high viscosity. High-viscosity lubricants are essential because they maintain a thick enough film of oil to support the weight and reduce friction between the moving parts. This is particularly important in slow-speed applications where the bearing does not achieve sufficient hydrodynamic lubrication, which can occur at higher speeds.

At low speeds, a thicker oil films the surfaces, preventing metal-to-metal contact and minimizing wear and noise. The high viscosity helps the lubricant adhere to the bearing surfaces and provides better cushioning, reducing the risk of damage. Other lubricant options like low-viscosity oil may not provide adequate protection at slow speeds as they can flow away from the contact areas too easily, increasing the chances of failure. Similarly, using grease or water-based lubricants would also not be suitable since they have different properties that do not effectively reduce friction in this specific scenario.