NANTeL Mechanical Engineering Certification Practice Test

Temperature affects how a lubricant behaves. The viscosity, or thickness, of most lubricants changes with temperature, so the lubricating film between moving surfaces can become too thick or too thin depending on how hot or cold the system runs. When temperatures rise, the oil often becomes thinner, thinning the lubricating film and increasing the risk of metal-to-metal contact, wear, and higher energy losses. When temperatures fall, the oil thickens, causing higher startup friction and slower flow until it warms up. A high viscosity index helps the oil keep a more stable viscosity across a range of temperatures, but the chosen lubricant must match the operating temperature range. Temperature also influences oxidation, additive effectiveness, and overall oil life, all of which affect performance and protection. The other options don’t govern lubricant performance: electrical resistance relates to insulation, color is mainly about appearance or contamination cues, and humidity affects corrosion risk more than the lubrication action itself.