Refrigeration Plant Operator B Practice Test

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What effect does an oil viscosity index improver have?

Reduces pour point
Increases resistance to oxidation
Maintains viscosity across temperature changes
Improves lubrication properties

The correct answer is: Maintains viscosity across temperature changes

The oil viscosity index improver plays a critical role in enhancing the performance of lubricating oils by helping to maintain a consistent viscosity across a wide range of temperatures. As temperatures rise, oils can thin out, leading to reduced lubrication effectiveness. Conversely, when temperatures drop, oils can become too thick, making them less effective in providing proper lubrication. By incorporating viscosity index improvers, the oil's ability to resist these changes in viscosity due to temperature fluctuations is significantly enhanced. This means that the oil maintains a more stable performance, ensuring effective lubrication under different operating conditions. Therefore, the primary function of a viscosity index improver is to ensure that the oil remains effective in lubricating machinery by performing consistently within a desirable viscosity range, regardless of temperature variations.