To prevent metal-to-metal wear, oil must have:

To prevent metal-to-metal wear, oil must have:

• A. Low viscosity to prevent wear
• B. Very low viscosity
• C. High enough viscosity to prevent metal-to-metal wear
• D. No viscosity requirement

Answer: (C)

The key idea is that keeping moving metal surfaces apart relies on a lubricating film whose thickness is governed by the oil’s viscosity. Viscosity is the measure of how thick or resistant to flow the oil is; higher viscosity means a thicker film forms between surfaces under the same load and speed. When the film is thick enough, the surfaces don’t touch, so metal-to-metal wear is prevented. If the oil is too thin (low viscosity), the film can break down under load and temperature, allowing surface asperities to contact and wear occurs. So, having an oil with enough viscosity to sustain a protective film under operating conditions is essential for wear prevention. Temperature and operating speed affect this requirement, which is why oils are selected to maintain adequate viscosity across the expected range.

The key idea is that keeping moving metal surfaces apart relies on a lubricating film whose thickness is governed by the oil’s viscosity. Viscosity is the measure of how thick or resistant to flow the oil is; higher viscosity means a thicker film forms between surfaces under the same load and speed. When the film is thick enough, the surfaces don’t touch, so metal-to-metal wear is prevented. If the oil is too thin (low viscosity), the film can break down under load and temperature, allowing surface asperities to contact and wear occurs. So, having an oil with enough viscosity to sustain a protective film under operating conditions is essential for wear prevention. Temperature and operating speed affect this requirement, which is why oils are selected to maintain adequate viscosity across the expected range.