A lubricating oil with high viscosity index is desirable for tractor engine due to
Options:
(A) More variation of viscosity with temperature
(B) Less variation of viscosity with temperature
(C) High pour point
(D) High cloud point
Official Answer Key:
B
Step-by-Step Solution & Explanation
Viscosity Index (VI) is a measure of how much an oil's viscosity changes with temperature. A high-VI oil maintains nearly constant viscosity across the engine's operating temperature range — desirable so lubrication is adequate both cold and hot. Answer: less variation of viscosity with temperature. Options (C)/(D) are unrelated properties (pour/cloud point relate to low-temperature flow, not VI).
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