A solid or semi-solid product of dispersion of a thickening agent in lubricating oil. Other ingredients imparting special properties may be included.
Classification of Lubricants
On the basis of its physical state, grease is classified as semi-solid lubricant.
Grease vs. Oil Lubrication – Advantages and Disadvantages
| Item | Grease Lubrication | Oil Lubrication |
| Feeding device | Grease sealed bearing does not require relubrication for an extended period. | Requires a device that continuously feeds oil (drip-feed, splash feed, recirculation system). |
| Consumption | Can be kept to the minimum necessary. | Significant amount required. |
| Lubrication system | Simple. | Complex. |
| Leakage | Unlikely because of its seal forming characteristics. | Possible if sealing system is adequate. |
| Use for high-speed application | Limited. | Yes. |
| Contaminant removal | No. | Continual removal by filtration or centrifuge. |
| Cooling efficiency | No cooling capacity. | High cooling capacity. |
| Friction loss | Generally high, but torque reduction can be achieved by channeling in roller bearings. | Generally low. |