Grease or Oil?
For an extensive period, the debate over the merits of grease versus oil as lubricants has persisted and continues to be a topic of contention. Each side presents compelling arguments and reasoning to support their preferences. Below are some classic arguments, as well as newer ones, gathered from both teams.
Team Grease advocates highlight several advantages. Grease exhibits superior stop-start performance compared to oil, as it remains in the component even when the machine is shut down, mitigating the risk of dry starts. It adheres well to certain parts like worn seals and connectors, reducing the chances of lubricant shortage and leakage. Moreover, grease prevents staining of the work product in applications like food, newsprint, and textiles. Surplus grease forms an effective sealant, preventing the ingress of particles and water. Regular regreasing also aids in removing contaminants from the working surfaces of components.
Furthermore, the inclusion of solid additives in grease, such as graphite, zinc oxide, or molybdenum disulfide, ensures they do not separate like some additives in oils. Properly selected grease maintains a reasonably low temperature, minimizing the risk of premature oxidation. Grease-lubricated applications with proper maintenance can operate for extended periods without the need for repacking bearings. Team Grease also argues that grease additives remain well-distributed and do not settle out during storage or machine downtime. Grease effectively immobilizes and localizes contaminants, keeping them away from critical surfaces. Competent lube technicians can safely introduce appropriate amounts of grease into bearings and similar components, resulting in long-lasting performance without the need for frequent repacking.
On the other hand, Team Oil asserts that oil offers superior flow properties, enabling efficient heat conduction and dissipation, which helps maintain stable base oil viscosity and reduces the risk of heat-induced oxidation and additive consumption. The lower energy consumption and heat generation in oil, compared to grease, are beneficial for gears and bearings. Oil lubricants eliminate the risk of incompatible thickeners clashing and causing consistency issues, as observed with some greases. Unlike grease, oil lubricants permit certain contaminants to be transported to filters, separators, and settling zones. Monitoring and controlling the oil volume in machine components can be precisely done, which is not as feasible with grease. Oil changes can be performed without the need for dismantling machine hardware, reducing labor, material, and downtime costs. Obtaining samples for laboratory analysis of wear metals, contaminants, and fluid properties is easier with oil-lubricated machines compared to grease-lubricated ones. Disposing of used oil can be accomplished in an environmentally responsible manner, whereas grease-lubricated systems are total-loss systems with no simple means of recovering and disposing of degraded or contaminated products. Additionally, oil systems like bath, splash, and circ-oil can lubricate immediately upon restart. The larger volume of oil used in certain applications allows for extended service life due to a higher supply of additives, and it facilitates the washing away of contaminants from frictional zones.
In contrast, regreasing practices may inadvertently drive contaminants into the core of bearings, leading to potential failure. Team Oil also highlights the effectiveness of soluble additives in oil formulations that provide comparable performance to control adhesive wear and abrasion in similar applications.
The debate between grease and oil remains multifaceted, and each lubricant option carries its unique set of advantages and limitations. Selecting the most appropriate lubrication method depends on the specific requirements of the application and the desired performance characteristics.
