How many factors are to consider when lubricating gear?

• A. Two
• B. Three
• C. Four
• D. Five

Answer: (C)

The main idea is that you must account for four essential aspects to keep gear lubrication effective. First, the mechanical demand on the gear—its load and speed—determines how much film strength the lubricant needs and how quickly heat is generated. Higher load or speed pushes you to select a lubricant with appropriate film-forming capability to prevent metal-to-metal contact.

Second, the thermal environment matters because temperature affects lubricant viscosity. As gear temps rise, a lubricant that’s too viscous can cause excessive drag and energy loss, while one that’s too thin won’t provide enough protection. Choosing the right viscosity grade ensures a stable film across the operating temperature range.

Third, the lubricant’s own characteristics—the type and viscosity and any additives—must suit the gear materials and loading conditions. The additives help with wear, corrosion protection, and film stability, while the base oil and viscosity determine how the film behaves under load and speed.

Fourth, the delivery and maintenance system is crucial. This covers how the lubricant is applied, the amount kept in the sump, and how contaminants are kept out. Proper application and cleanliness prevent film breakdown and abrasive wear, ensuring the lubricant stays effective over time.

Essentials are captured by considering these four areas together; ignoring any one can lead to inadequate protection, either from too thin a film, excessive drag, or contaminated lubricant.